Surface Hub reservation requests from on-premises accounts don’t get processed

A quick write-up for something I came across today.

When you have a Exchange Hybrid deployment and users with their mailboxes housed on-premises aren’t able to book the Surface Hub then check if the Room Mailbox accepts “external meeting messages” with this PowerShell command from Exchange Online:

Connect-ExchangeOnline

Get-CalendarProcessing SURFACE HUB ACCOUNT | select ProcessExternalMeetingMessages

If the answer is “FALSE” then change this value to TRUE

Get-CalendarProcessing SURFACE HUB ACCOUNT | Set-CalendarProcessing -ProcessExternalMeetingMessages $true

And your issue has been resolved!