OK Team,
I think I fixed mine (sort of). The Microsoft Bookings was a good clue for me. When if I disable my Bookings page and tried again, it got closer. I got an error instructing me to relog into my personal account. I'm not sure why that was there at all, but I went to Settings: Calendar: Accounts and removed the one with the error. Then all my calendars came back!!!
Hope this helps some of you. Your results may vary! Please update the thread with your results for the group.
Good Luck!
-E
I tried this with a couple more users here and I think it has more to do with the Settings - Calendar - Accounts than the Bookings page.
Good Luck!!!