There was a little red exclamation point in a circle in my calendar app and when I click on the calendar (when yahoo was there) it said unable to connect.
When I went back in after deleting the account and re-adding I had to physically “add another calendar” by typing in yahoo and still then the calendar did not appear however several other calendars were clicked under yahoo that I never added they were a series of numbers and letters that made no sense to me.