Configuring Teams calendar access for Exchange on-premises mailboxes

Unfortunately, no option to reply to specific comment now.  khalednafea  - answering your question "Calendar Tab appear but keep loading and it didn't show any data i check logs Calendar App was there and isMailboxDiscoverable: true but i see below error , any idea ?" 

Unfortunately I cannot tell what's wrong, as i don't have any information regarding your environment. Please, try to check all the settings according to the article on How to configure OAUTH. In pervious versions of HCW we had some issues, when we needed to configure some setting manually. I don't have opportunity to verify specific build that was used,  last time it worked for me. If you will have some more info from test-oath... and exrca, you can share it with us, if it's OK for you. have a nice day!