I’ve come across an issue where the customer could not enable contact sync in the Outlook app inside a work profile.
When a used would go into Outlook app and hit “Sync Contacts” the contact sync the switch would turn on and then instantly turn off.
This was due to a permission issue.
Even though the customer had a global “Auto grant” permission setup via a configuration profile this was not sufficient.
Additional contacts permissions had to be added
This is done from Client Apps -> App configuration policies