Lightroom Classic 9.3 Stuck Syncing. Major Problem

You show screen shots of Lightroom Classic which is the traditional version of Lr but you say "Lightroom Desktop" which now a days refers to the newer version of Lr that is Cloud Centric. You also show that your Adobe storage space is 1 (ONE) Tera Byte which comes with the Lr Cloud Centric program normally.

Then there is LrM for iOS and Android Mobile Devices. Which you show you have several listed in the "Folders" section of the left hand side panel and then only a small section of the Collections section that is not showing any collection are synced.

So PLEASE state the Exact versions of Lr you are using on all your Devices.

It seems you are using both LrC and LrD (Desktop, Cloud version) on Real computers and LrM on your mobile devices.

What I think is you have just To Much Stuff going on for Lr (whatever version) to keep track of.

It is NOT Wise to have both LrD and LrC installed on the same computer and trying to sync both up to the Lr Web system and to the mobile devices and back again.

I have been doing some searching and cannot find anything definitive to remedy your problem. See the link below for more info about things to try.

https://lightroomkillertips.com/sync-stuck/ 

If you have to resync the bulk of your collections I would create smaller collections and and beginning syncing them in batches.

Sync only image files and video files will be sync.

Your screen capture shows that you have selected ”previous import” that is not a folder on your operating system and does not contain the actual image files. The actual image files should be in a folder or maybe several folders in your operating system which should be displayed in the Folders section in the Library module.

Are you talking about syncing the files to the Creative Cloud storage?

If so then the normal procedure in LrC is to select the files from the folders and place into collections and then

click on the far left of the collection to start syncing.

You activate syncing to the creative cloud by signing in to your Adobe ID. See the screen capture.

Also, see this link for more info.

https://helpx.adobe.com/ca/lightroom-classic/help/lightroom-mobile-desktop-features.html 

I'm not going to be a lot of help, I'm afraid. But from my experience that seems to be a big chunk to try to sync all at once. I am primarily a LrC user, and synchronize a few collections now and then. But I think if you break them down into smaller collections you might have greater success.