IOS Photos app stopped syncing properly

[Acmartina]

I am struggling with a Photos sync problem with my MacBook Pro (M1 Max, 2021, 32MB, 2TB HD). My photo library sync’s fine with my iPhone and iPad, and it used to sync fine with my MacBook, but it started having problems about a year ago. It would take longer and longer to catch up on my MacBook. I tried a number of things (see below) but it sort of stopped around April 2023 and no matter how long it sits there saying “Syncing iCloud …”, or whatever fixes I try, no new photos or videos appear. Everything is fine on iCloud.com, iPhone, iPad. Just won’t catch up on the MacBook (since April). Some obvious things -

• I have plenty of available space on my HD (700+ GB)
• and on my iCloud storage (1 TB).
• Internet is fine (600+ Mbps).
• Photos all show up on iCloud, iPhone, and iPad.
• Activity monitor shows nothing really sucking up CPU or memory.
• OS is up to date (14.1.2)

I have scoured the internet for articles and keep getting the same suggestions, none of which work. The most comprehensive article I found is here, so I’ll use that to check down everything I’ve tried.

14 Ways to Fix iCloud Photos not syncing on your Mac

1. Check the Sync Status - Currently (and always) says "Syncing with iCloud …"
2. Activate iCloud Photos - Always been activated with "Optimize Mac Storage" option. I could try "Download Originals" I suppose, but that seems a waste of time
3. Check your Apple ID - Yes I am using the correct Apple ID.
4. Force Quit the Photos App - I have tried this many times. Just continues on with "Syncing with iCloud …" as before.
5. Check your internet connection - No problems there. At the moment 617 Mbps (Latency 14 ms). No download problems with anything else.
6. Turn off low power mode - Done for plugged-in mode, which is most of the time. No difference.
7. Charge your device. Fully charged. No battery or power adapter problems.
8. Check the iCloud System Status. No issues.
9. Restart your Mac. Many times
10. Free up some storage space - 700+ GB available on HD, 1 TB available on iCloud. Photos are taking up 411 GB on iCloud. So plenty of space everywhere. And all photos sync fine on iPhone and iPad.
11. Flush the DNS Cache - Did this once. No change and took an annoyingly long time to recover.
12. Repair the photo library. This is a long and tedious process and had no affect, but I have done it a couple of times. Again, no problems with iPad or iPhone, and MacBook is set to "Optimize storage" rather than "Download originals" so local version is smaller.
13. Delete the Sync Index. Did this once. Took weeks to recover!! Not trying that again. No change.
14. Update MacOS. Currently up to date. This problem has been going on since April 2023, through multiple updates.

Please, please offer any new ideas. I am getting very frustrated because I really need to have the photo library available on the MacBook for various applications and the work-around are very tedious

Thank you,
Steve