Outlook Calendar failed again

I noticed today that an expected calendar item wasn’t showing up in eM Client and one which I amended earlier this week had not been amended. Although I initially assumed I had made a mistake, a quick review showed that virtually ALL my calendar entries over the next few months were missing in eM Client - a few were showing up, but only about 10% of them. I opened Outlook and checked and all of the items ARE still showing up there so it seems eM Client isn’t syncing properly. I added the missing entry (in Outlook) which originally caught my attention and that one DID immediately sync and show up in eM Client too - but all those other ones are still absent. I restarted and checked for updates on both but the issue still persisted.
It’s not actually a major issue for me as a long time ago I decided that electronic calendars can’t be trusted so I mainly rely on my paper calendar. eM Client and Outlook are simply my back up - this is another example of why!