Hi @IBN ,
We are on exchange 2016 hybrid configuration some users can't load their calendar on teams.
By "can't load their calendar", do you mean these users cannot see the Calendar button on the menu options in Teams?
Do the affected users have anything in common? For example, are they all hosted on Exchange on-prem?
Please have a check via the Teams web client and see if the issue persists there.
Furthermore, it's recommended to follow the troubleshooting steps listed in the document below:
Troubleshoot the Teams calendar App issue
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