iCloud photos do not synchronise on macbookpro
I am using a MacBookpro on OS 12.7.6. I am taking pictures on my iPhone 13 and these synchronize automatically on my iCloud.com - no problem there (the iCloud has 85GB free memory space). Normally the pictures automatically synchronize on my MacBook once I open the photos app. Today this does not happen. the app says it needs to synch 1953 pictures and stays there for days. The only option is to interrupt it.
I already unset the iCloud synchronization in photos and reset it again, it restarts the process but without doing any downloads.
What is going wrong?
MacBook Air 13″, macOS 12.7