Out of no where, my 2017 MBP 13" with Catalina (10.15.6) started asking me to provide my iCloud password. Every time I entered it, it gave me “unknown Verification” error. The same login worked on iCloud.com and other devices. Long story short, called Apple support and wound up re-setting my keychain and I got back in. But I still think there are corrupted files somewhere. Biggest annoyance is I can’t connect to my iPad Pro 11" 2019 with SideCar where it used to work before. I use this in my WFH workflow. It doesn’t even show up as a device in the Sidecar System Prefs pane.
Did everything it says in Apple Communities - Toggled WiFi, Toggled BT, rebooted both devices umpteen times. I am logged into same iCloud account.
Any MPU’rs have some ideas of where I might look to delete some demon .plist or something?