The Photos app crashes when I try to enable iCloud
A few weeks ago, the Photos app on my MacBook stopped getting my latest photos. The photos were getting from my iPhone to the iCloud, but were not syncing to my MacBook. This was after several months of all syncing working well. To remedy the problem it was my intent to disable, then re-enable iCloud for Photos on my MacBook. FYI, I have several other iCloud data stores including Contacts, Drive, Notes, etc, which are syncing properly.
The problem: I open Photos preferences and select "iCloud Photo Library" (see first attached pic). A dialog box first tries to up-sell me more disk space (even though I have twice what I need at 50 GB). Upon selecting 'Continue' from that dialog (see 2nd picture), the Photos app crashes immediately. This has been going on for several weeks. I've been waiting / hoping for a software update to fix this but no luck.
Today is March 23, 2021.
I'm running macOS High Sierra 10.13.6.
Photos application Version 3.0 (3291.13.230)
All software is up-to-date.
Help appreciated.
MacBook Pro