Lightroom Classic ↔ Cloud sync stops at 2,716 of 32,585 cloud assets — Rebuild Sync Data and local cache reset did not restore missing assets

Hello Adobe team,

I am posting here because I am unable to resolve a persistent Lightroom Classic ↔ Lightroom (cloud) synchronization issue after multiple troubleshooting attempts, and I would appreciate guidance from an engineer or someone who can escalate this if needed.

## Subscription context

I have been an Adobe photography subscriber continuously since approximately 2017, originally through the standalone Lightroom mobile subscription purchased via Google Play. In June 2023, I deliberately migrated to the **Creative Cloud Photography plan with 1 TB** specifically to gain the bidirectional synchronization between Lightroom (cloud) and Lightroom Classic - that capability was the entire reason for the migration, since I wanted to keep editing on a desktop in Classic while having all assets and edits accessible on mobile and on the web. Reliable two-way sync is, for my workflow, the core value of the plan.

## Why I am only now setting up the full Classic ↔ Cloud bridge

I want to address this proactively to avoid any assumption that this is a new account or a small library. The cloud library has been built up steadily since 2017 - it represents close to a decade of personal and travel photography that I care a great deal about. I migrated to the 1 TB Creative Cloud Photography plan in 2023 specifically to unlock the Classic side of the workflow, but until recently I did not have a desktop machine powerful enough to host a Lightroom Classic catalog of this scale and run my editing workflow reliably. Now that I do, I am finally trying to bring the full cloud library down into Classic so that I can edit on the desktop while keeping everything accessible on mobile and on the web. So this is not a stale or abandoned account - it is an active, long-standing library that has only just reached the point of needing the Classic side of the sync to function end-to-end.

## Important: the cloud library must not be wiped or reset

I want to state this very clearly up front, because I have seen it suggested in some community threads and I want it on record before any troubleshooting is proposed:

**Under no circumstances do I want the cloud-side library deleted, "reset", or rebuilt by re-uploading from Classic.**

The cloud library is the authoritative copy from my perspective. It contains close to a decade of photos, organization, edits, and album structure that I do not want to risk losing or having to recreate. Yes, I do maintain local backups (an external drive copy and a separate folder copy on a second internal drive), but I treat the cloud as a peer master - not as something disposable that can be regenerated from a local snapshot.

Any proposed fix that involves "delete everything from lightroom.adobe.com and re-

upload" is not acceptable to me as a solution. I am specifically asking for a fix that brings the existing 32,585 cloud assets down to Classic, not one that destroys them to start over.

If a server-side action is needed, I would like to understand exactly what it does to the cloud-side data before it is performed, and I am happy to wait for the right person to handle it rather than have it done quickly with risk.

## Current state

- **Cloud library**: 32,585 photos, approximately 669 GB used of the 1 TB plan
- **Lightroom Classic catalog**: only 2,716 photos appear under "All Synced Photographs"
- **Local sync target folder** (`D:\LightroomSync\`): 5,416 files (~83.6 GB) - includes XMP sidecars
- **Missing**: approximately 29,869 cloud assets that Classic does not appear to know about
- **Sync status icon**: shows "All synced" / "Synced" with no pending downloads, even though the vast majority of the cloud library has never been downloaded

The "From Lightroom" collection group is present in the Collections panel and contains all of the date-named album shells, but almost all of them show "0 photos" - only a handful (e.g. one labeled "suisse" with 1,348) contain anything. So Classic has received the album metadata, but not the asset list inside them.

The system is reporting sync as complete while clearly being far from it.

## What the Lightroom Sync Diagnostic Log shows

I generated a Sync Diagnostic Log from within Lightroom Classic (Help menu). The HTML report contains a section "Sync Pending Downloads" with the table headers `document id | sync status | filename` and **no rows underneath** - Classic's sync engine has an empty download queue.

The associated logs in the diagnostic ZIP show:
- `Blob DB service is not initialized` (in `read_embed_sidecar_table_failure.log`)
- Repeated `NotFound` entries in `big_data_db_haskey_file.log` and `big_data_db_retrieve_file.log` referencing the Pixel-Masks DB path
- No `ERROR`, `failed`, `404`, `403`, or `throttle` matches in the main Lightroom logs

The catalog itself is healthy: `Lightroom Catalog.lrcat` is approximately 554 MB, the `Lightroom Catalog.lrcat-data` folder exists, and the `Managed Catalog.mcat` in the sync data folder is approximately 839 MB. The local sync database does not appear to be corrupt in the sense described in https://helpx.adobe.com/lightroom-classic/kb/local-sync-database.html - Classic does not display the "local sync database is damaged" dialog at startup, so that recovery procedure does not directly apply, but I want to flag that I have read it and I am aware of the `.wfindex` / `.mcat` deletion procedure described there.

## What I have tried (in chronological order)

1. **Standard suspend / resume** of sync from the cloud icon - no change.
2. **Quit and restart Lightroom Classic** multiple times - no change.
3. **Sign out / sign back in** from the cloud icon - no change.
4. **Rebuild Sync Data** (hidden option exposed by Alt-clicking in Preferences → Lightroom Sync) - this temporarily resumed activity for a short period and brought the local count from ~436 to ~2,716 photos, after which sync stopped again with status "Synced" despite tens of thousands of cloud assets still being absent.
5. **Renamed `Lightroom Catalog Sync.lrdata`** to `.OLD` and **renamed `%LOCALAPPDATA%\Adobe\Lightroom\Caches\Sync Data\user`** to `.OLD` while Classic was closed, then reopened Classic so it could rebuild both from scratch. Both folders were recreated (verified with PowerShell: new `Lightroom Catalog Sync.lrdata` at 15:00:24, new `user` folder at 15:00:10 on the same day). Result: sync re-initialized, immediately reported "All synced", downloaded zero new photos.
6. **Verified network connectivity** to Adobe sync endpoints (`lightroom.adobe.com`, `photos.adobe.io`, port 443) - all reachable.
7. **Verified the cloud library on lightroom.adobe.com via web browser** - all 32,585 assets are visible, the storage usage of ~669 GB is shown, no account warnings, no error banners.
8. **Verified the option "Store a copy of the original raw file locally"** is enabled at the collection level for the "From Lightroom" collections that contain photos. The right-click menu does not expose this option on the parent group, only on individual child collections.
9. **Checked Windows power settings** - sleep disabled, machine plugged in, no network interruptions during sync attempts.
10. **Checked for stale "stuck" assets** - I previously identified one photo that Classic was stuck attempting to download. I deleted that asset from the cloud via lightroom.adobe.com. The stuck state cleared but the broader incomplete-sync issue did not.
11. **Reset Lightroom preferences** (renamed preferences folder so Classic regenerates them) - no effect on the sync behavior.

The local-sync-database article in the Help Center addresses the case where Classic refuses to launch due to a corrupted sync DB. In my case Classic launches normally and reports sync as complete - the failure mode is silent rather than fatal, which makes it harder to fall back on the documented `.wfindex` / `Managed Catalog.mcat` deletion procedure with confidence that it will help (and I do not want to delete `Managed Catalog.mcat` without guidance, since the Help article itself warns that this can cause loss of unsynced local data).

## What I believe is happening

Based on the diagnostic log and the behavior, my best guess is that on the **server side of my account**, the asset index that Classic queries to enumerate "what needs to come down" is returning a partial or truncated response, after which Classic considers itself caught up. Every local reset I have done has rebuilt the local index from that same upstream response, so the local-side fixes converge to the same incomplete state.

If that interpretation is correct, this is not something I can fix from the client side - it would require someone with access to the account's server-side sync index to refresh or rebuild it, **without altering or deleting the underlying cloud assets**.

## What I would like

1. Confirmation of whether a server-side rebuild of the account sync index (one that re-enumerates assets to Classic without modifying or deleting them) is something Adobe can perform.
2. If yes, the appropriate channel to request it (I have a Sync Diagnostic Log ZIP ready to provide privately to whoever needs it).
3. If no, a clear statement of which client-side procedure has the best chance of forcing a full re-enumeration of the 32,585 cloud assets, and whether deleting `Managed Catalog.mcat` (as in the Help article) is recommended in this specific scenario.

To repeat the boundary I set out above: any proposed solution must preserve the cloud library as-is. I am asking for a path that pulls the existing cloud assets down to Classic, not one that uses Classic to overwrite or replace the cloud side.

I am happy to provide the diagnostic ZIP, additional logs, screenshots of the cloud icon panel, screenshots of the empty "Sync Pending Downloads" table, and PowerShell outputs of file counts/sizes through a private channel.

Thank you for any guidance. I want to keep using this ecosystem - moving to the 1 TB plan was a deliberate choice precisely for the Classic ↔ Cloud bridge - but at the moment the sync side of that bridge is not functioning for a library of this size, and I have exhausted the documented user-side procedures.

Lightroom Classic version: 15.3 (Windows)
Operating system: Windows (current)
Library context: ~32,585 cloud assets, ~669 GB cloud storage used
Local result: ~2,716 photos visible in Classic, ~5,416 files in the sync target folder