OneDrive app on the MacBook Air doesn't want to let me log in, so I've deleted it & its corresponding synced files in the Home folder. Instead, I have created a single site browser of OneDrive using Epichrome app. This at least gives me access to my content. No such problem with the iMac.
Opened Keychain & deleted the OneDrive Cached file therein, as recommended by MicroSloth, didn't work.