Using Classic Outlook on Windows for personal email, calendar, and contact management
Hi Daniel
Microsoft have come back to me with this which includes a link to what was released :-
Hi Lia,
The issue is solely related to Outlook showing the warning message "Trying to retrieve...", issue is not happening to Outlook on the Web.
When you go to the browser Outlook.office.com, you are not getting the same error message. Therefore, this is not related to Exchange Online server issues or mailbox issues.
Issue is only happening to Outlook. The link I provided to you below is about the Office update that directly affects the Outlook.
https://learn.microsoft.com/en-us/officeupdates/update-history-microsoft365-apps-by-date
I provided it to you as requested as in the call you told me that you will try to uninstall the update to one of the PC.
Lia