I have a bit of a strange situation. I am currently in the middle of migrating users to Office365 from an Exchange 2019 Environment.
If I move a mailbox using the O365 Migration Batch Wizard, on-prem users can not see their Free / Busy information.
If I move a mailbox using PowerShell (New-MoveRequest), on-prem users cannot see their Free / Busy information.
I have proven the issue only exists when I use PowerShell as I have moved one of my accounts back to on-prem and then used the migration wizard and now the Free / Busy is working as expected when an on-prem user tries to view it.
I have checked all the settings of an account that works and an account that doesn't and I can't see any obvious differences and I can't seem to find anyone who has had a similar experience. Has anyone else seen this or can point me in the right direction of how I can resolve this without moving all the accounts back to on-prem and then using the batch migration wizard (There are a lot of accounts already moved).