Outlook Calendar

Using Shared Outlook Calendar on 

Microsoft® Outlook® for Microsoft 365 MSO (Version 2212 Build 16.0.15928.20196) 64-bit

If I save an event in the shared calendar it looks as if its saved then as soon as you move cursor away it disappears. If I save an event on outlook app on android on the same calendar in the same way its fine.

It has only happened in the last week or so. Is this a problem with the new shared calendar improvements ?