Logged out/in of Apple ID, now my iCloud is empty

After logging out of my Apple ID because there was a notice in Sys Prefs > Apple ID that I had to do so to reactivate something or another, when I logged back in, the iCloud Drive on my computer is completely empty — even though when given the "If you turn off iCloud Drive, all documents stored in iCloud will be removed from this Mac" pop-up during logout, I selected to "Keep a Copy" the files in iCloud Drive.

The files are are still there at iCloud.com, but everything has disappeared locally (screenshot below).

I can add files and folders to the iCloud Drive in my Finder, and they appear on iCloud.com, but everything else I can see on iCloud.com is not.

The syncing-progress icon next to iCloud Drive in the sidebar shows maybe 2%, and does not change. When I mouseover that icon, it gives me an (i) info icon, but clicking it does absolutely nothing. (By the time I finished writing this, the progress icon had disappeared.)

If I try go to Sys Prefs > Internet Accounts > iCloud and uncheck iCloud Drive, it tells me "iCloud needs to finish updating before being turned off" and shows a progress bar with maybe 1% progress — even though it's now been an hour since I logged back in.

Any suggestions?

2020 M1 MBA 11.6.1