What kind of Office 365 scenario do you use?
- Pure Office 365
- Office 365 with additional on premise services (e.g. AD Sync, Exchange on-premise)
- Exchange 2019/2016
Does the Button work for some users or none?
Are there commonalities of the affected users, e.g.
Exchange server (O365 type mailbox or on-premise)
(Local) security policies
What ist the system configuration of the affected users:
Operating system version
Does the button work in Outlook Web Access?
Does the button work in the local desktop client of Outlook?
If an error occurs, what is the error message?
Is the access to the required domains valid?
Which kind of deployment method did you use?
Installation via Exchange Admin Center, Office 365 Admin Center, or local client?