A Teams cutover which has been syncing with no issues is now failing the cutover with errors such as.
Graph API error for ODfB Sync - access denied
Problem copying team channel messages 'Teams Folder name', or no permission
Status Code: Forbidden
Microsoft.Graph.ServiceException: Code: Forbidden
Message: Failed to get license information for the user. Ensure user has a valid Office365 license assigned to them.
A sync uses the PowerShell account whilst the cutover uses the service account to migrate additional data.
The issue can occur when the service account doesn't have the required permissions.
1.) The Service account has got a Mailbox ie licensed, both source and Target
2.) Service account needs to be a Team and sharepoint admin
3.) Service account must be teams enabled
If any changes are made to the accounts, then run a Reconnect to the tenant to refresh the token.