Teams / Exchange Server OAuth broken for calendar delegation?

[MaximeRastello]

We have configured OAUTH between Skype for Business Online and Exchange Server to be able to generate Teams meeting invitations for calendar delegation.

The configuration was successful and working for several months until June 12th. Several customers reported that generating Teams invitation for delegates does not work anymore from the Outlook Windows client.

Any issue in the backend recently?

[#2]

HI,
one of our customers has got the same issues in an Exchange hybrid enviroment after working fine for about half a year.

Some Exchange Online users can always use calendar delegation, some never can, despite having the correct permissions which were also recreated.

E.g. we have a delegator with 3 delagates, one is working fine all the time, two cannot schedule a teams meeting in behalf of the delegator.
Workaround doing this in owa for exo mailboxes works fine.

This started approx. on August 14th 2023, no changes were made on our side.

Also we have the same behavior with a stable working OAuth integration to onpremises, some delegations are still working, some not.

Since this week some random users which were working fine cannot delegate one day and the day after everything works fine again.

Atm we are circling around with microsoft unifying support, after some days of rereating the same permissions via exo powershell I will transfer again all Teams logs to support.

[#3]

@MaximeRastello

@Steven_Koppers

We are currently having similar issues and I was wondering if you found a fix for that case already.

We are having the exact same scenario as both of you do.

[#4]

@JanV0 

We are having issues with an older Version of MS Teams (version 1.5.xxx) in combination of an older version of Outlook 365 (ca. January 2023).

With the actual MS Teams Version I think 1.6.00.24065 of September 2023 and an up to date MS Outlook 365 there were no issues anymore.