iMac 27" Sonoma will not sync iCloud Photos with new library

The Photos app on my iMac started showing blank photos and giving errors. Eventually giving me "photos the library could not be opened -1" and a "phphotoserrordomain error -1" messages.

I have followed numerous threads with repairing the library, turning iCloud on/off, turning photo sync on/off etc. Eventually I just deleted the broken library, turned sync off, rebooted, turned it on again, and after it prompted me to start a new library ... it does nothing. It says in big bold letters "Syncing with iCloud", but after letting it just sit..nothing. If I restart Photos I get a blank screen. If I turn sync off/on again, the cycle continues.

My photos in iCloud seem fine. I can see them on all my other devices, I can log in to iCloud.com and I can see all my photos there as well. It's just my iMac that seems to be the problem. Other iCloud services seem to work fine.

Not sure how to go from here.