Adding Teams-meetings as a Delegate not working after latest Exchange 2019 October update

We noticed that since the install of KB5066367 update our users cannot schedule any teams meetings for delegates. How is that possible, nothing has changed from our side besides this update.

Error when using the Testing Teams Meeting Delegation on testconnectivy.microsoft.com:

--error--

Testing if the Teams Meeting Scheduler service allows user ******@xxxxxxxx.xxxx to schedule a Teams meeting on behalf of user ******@xxxxx.xxxx.

The delegate is not allowed to schedule a Teams meeting on behalf of the delegator. You can share the logs below with Microsoft Support for their investigation.

 Tell me more about this issue and how to resolve it

Additional Details

TelemetryId:

41e2019c-3bc9-4cc6-9146-d4e07b6f64d1

Timestamp (UTC):

2025-11-17 14:06:22Z

Teams Meeting Scheduler Service response:

{"debugMessage":"Exception of type 'Microsoft.Skype.SkypeCast.SkypeCastCommon.Exception.CustomizedHttpResponseException' was thrown.","meetingType":"","errorSubCode":4014,"statusCode":401,"additionalInfo":""}.

--error--

When someone with delegate access wants to create a Teams meeting with the button in Outlook (Teams-addin) it says "

To schedule a Teams meeting, make sure you're signed in to Teams". Scheduling in own calendar just works fine.