Teams Attendance Report - A Network Error Occurred

Hi all.

Could anyone shed some light on an issue I have reported that is affecting all users, please?

When a user accesses meetings they arranged, either at the time of the meeting or afterwards, they get the following error:

All these users are on the same meeting policy so I have checked:

[PS]> Get-CsTeamsMeetingPolicy -Identity RestrictedAnonymousAccess | Select AllowEngagementReport

AllowEngagementReport
---------------------
Enabled

I have made a comparison using fiddler to a working tenant and the tenant displaying the global issue, and I see one obvious difference:

The working tenant shows HTTP traffic to api.cortana.ai but the tenant with issues shows no trace of this api.

This feature worked on the affected tenant until around 4 weeks ago but would love to see if anyone could steer me in the direction of what could have caused this to stop working?

Any help is gratefully appreciated. 

Thanks