As you may be already aware, OneDrive for Business is using the user principal name (UPN) to provision the personal space, and as such the UPN is also used in the URL for accessing it (like https://mytenant-my.sharepoint.com/personal/user_upndomain)
As such, any change of the UPN’s user has an impact on OneDrive for Business and can broke synchronization.
An updated OneDrive for Business client (starting with build 18.212.1021.0008) is being pushed to automatically taking care of this UPN change impact. This means OneDrive for Business client will update the synced OneDrive URL to the new one after the UPN has changed.
There is still some impacts (as expected with such important change):
- Any shared documents/folders on OneDrive for Business will not be shared after the change. It will be required to share them again
- Any workflow or SharePoint Apps referencing the OneDrive for Business URL will no longer work after the change. You will be needed to manually update this reference
While the UPN change is being propagated within the Office 365 environment, user may got some error like “You don’t have permission to sync this library” or “One or more libraries could not be synced”. A simple restart of the OneDrive for Business client will fix it once the UPN change has been completely propagated.
The recommendation (as for any change which can have big impact) is to do such change during non business hours.
