PROBLEM SOLVED with the VERY LATEST Beta Channel version of Outlook 16.57 (V220.11101) I just checked this worked NB. I had to force a re-index of spotlight. NB. This is the Classic NOT New Outlook

My mistake - I had an isssue with loading a Gmail account on this M1 and I used IMAP, now for some reason I can select a Google account and then the calendar appears