iCloud Photos for Windows won't update

FWIW:

My photos synch between my iphone, ipad, web (icloud.com) almost immediately. The issue is with the iCloud for Windows app. When I right-click the app icon in the notification bar area, it shows that iCloud Drive is updated (so many minutes ago) but not Photos.

And yes, I have read available documentation. I didn't want to "Sign Out" from the app because it said it would delete all the photos. Since nothing seemed to work, eventually that's what I resorted to. I Signed Out and that did indeed delete all the photos. I signed back in and then that started the resync process.

The problem here is that I have a few thousand photos. That resync process takes a LONG time... I ended up leaving it alone overnight to download photos again. A day later, there are still photos w/ the little could icon, not the green checkmark, but there is no activity (no downloading or other network traffic). So I'm not sure why that is or how to, once again, for the iCloud Photos folder to "refresh" or "complete" whatever it's doing... I take it the "for Windows" app is just not to be considered useable or reliable?

Also, I should note: I rebooted my PC. And now all the files list in the iCloud Photos directory are showing with the "Sync pending" icon and the internet traffic and PC are trying to chunk through several thousand files again.

I have more than enough free disk space (about 1.5 TB!). As I said, on the first download (after signing out, then back in), there were quite a few items with the green checkmark, many w/ the cloud icon. After a PC reboot, ALL the files show the same "sync pending" icon. And I'm back to that state where when I right-click the app icon in the Notification area, it shows that Photos has not updated essentially since my last reboot, however Drive has updated in the "[so many] minutes ago" timeframe.