Outlook IOS Calanders not synching/blank

[Sheridan]

We have a bunch of iPads (11th gen) managed by Mosyle with the MS apps installed. Our users sign in to their Outlook app with their school account and that works fine for email etc. However we've noticed the calendars aren't populating and no events are shown

 

They can see the calendars for their account when they go into the settings to pick the default (such as Tiemtable, Calendar etc) but whatever they pick the calendar ends up showing nothing

 

We have a pretty light policy applied to these in Mosyle and the only setting I can possibly think is an issue is the one we enabled to prevent them signing in with their Apple ID which we can't switch off - and surely this wouldn't affect the Outlook app?

 

So it seems Outlook will only pull down the personal Calendar and not any additional calendars associated with that account, even though it shows them in the selection list?

 

Edited May 14 by Sheridan