HEVC codec won't install (mc_enc_hevc.dll, AdobeInstalledCodecsTier2): Process Monitor proves Premiere never even attempts the write. Pr 26.3, Win 11. Every standard fix ruled out.

Posting after an exhaustive diagnosis session with Process Monitor proof, hoping it reaches Premiere engineering. Every standard fix is ruled out and the root cause is inside Adobe's own code.

ENVIRONMENT

- Windows 11 Home, build 26200

- Premiere Pro 26.3.0, Media Encoder 26.3.1, After Effects 26.3

- Paid, genuine, signed-in Creative Cloud (executables validly signed by Adobe Inc., no patchers, hosts file clean)

- Codec folder: C:\Users\Public\Documents\AdobeInstalledCodecsTier2\4.3

SYMPTOM

Any HEVC / H.265 clip (decode preview or export) throws three dialogs:

1) "Unable to install: ...\AdobeInstalledCodecsTier2\4.3\mc_enc_hevc.dll ... make sure you have write access to this location and sufficient hard drive space ..."

2) The same dialog for mc_dec_hevc.dll

3) "This file requires the HEVC codec which is included with a Creative Cloud membership ... ensure you are connected to the internet for the HEVC codec to install correctly."

H.264 works perfectly. Only HEVC fails, across many projects, over a long period.

KEY FINDING (Process Monitor)

Captured a 1,621,736-event trace during an HEVC import. Filtered to the codec folder, the ONLY operations Premiere performs are read checks:

  CreateFile ...\4.3\mc_enc_hevc.dll  ->  NAME NOT FOUND

  CreateFile ...\4.3\mc_dec_hevc.dll  ->  NAME NOT FOUND

  CreateFile ...\4.3 (the folder)     ->  SUCCESS

Across all 1.6M events there is NOT ONE write attempt to that folder by any process: no WriteFile, no create/overwrite disposition, no rename, no delete, no ACCESS DENIED. So the app checks whether the DLL exists, finds it missing, and reports the "unable to install / write access / disk space" error WITHOUT EVER ATTEMPTING TO UNPACK OR WRITE IT. The failure is entirely upstream of the filesystem, inside the licensed codec provisioning (the decrypt/unpack of the packed "WIN1" mc_enc_hevc.dat / mc_dec_hevc.dat). The dialog's mention of write access and disk space is misleading; there is no disk write at all.

ALREADY RULED OUT WITH EVIDENCE (please do not suggest these)

- Disk space: failed with 143 GB free.

- Write permissions: test files write into the 4.3 folder and persist; ACL clean and inherited; procmon shows the folder opens SUCCESS.

- Antivirus: only Windows Defender, zero detections, Controlled Folder Access off, no ASR rules.

- Network/entitlement: the OptionalHEVCCodec package downloads fine (per DLM.log); the packed .dat sits locally in Premiere, Media Encoder, and After Effects.

- VC++ runtime current (14.50.35719).

- Public Documents not redirected; %PUBLIC% correct.

- Full Creative Cloud Cleaner Tool removal of Premiere + Media Encoder + shared components, then a clean reinstall: no change.

- UAC raised from Never notify to default + reboot: no change.

- Brand new Windows administrator account, signed into CC, HEVC import to trigger: folder still empty (machine-wide, not a user-profile issue).

- Machine-level license cache reset (renamed SLStore, SLCache, NGL, OOBE; reboot; CC sign out and back in): the caches rebuilt clean and the codec still would not unpack (so not a corrupt license cache).

WHAT I AM ASKING

Since Premiere never even attempts the write, this cannot be fixed by any local change (permissions, disk, antivirus, license). It is inside the codec provisioning. Ideally either:

1) provide the two unpacked DLLs (mc_enc_hevc.dll and mc_dec_hevc.dll, the 4.3 version Premiere 26.3 expects) so I can place them manually, or

2) escalate to engineering to fix the decrypt/unpack step for this machine.

Full 286 MB Process Monitor capture available on request. Thank you.