iCloud Drive won't sync to Mac

In 20 years I've gone through a lot of Macs but this is the first time this has ever happened and I uninstall/reinstall macOS quite often. I added myself as an Admin account to my wife's iMac. Installed the apps I wanted, Photos synched 5K pictures just fine, but when I go to iCloud Drive in Finder it's empty. It doesn't say "Synching"...it's simply empty.

At iCloud.com iCloud Drive is just fine...all my folders and files. In the Files app on my iPhone...no problem, everything is there. I tried restarting, signing out of iCloud and back in (twice), checked, unchecked and checked again the iCloud Drive box in Preferences|iCloud. It's just not synching. Any ideas?