ERROR (ThrottledFolderBind): Exception calling "Bind" with "3" argument(s): "The request failed. The remote server returned an error: (401) Unauthorized.

[creverythingt]

Trying to use Merge-MailboxFolder.ps1. OAUTH has been configured as per the guide. I'm logging into the browser, obtaining a token and receiving the error as per title:

ERROR (ThrottledFolderBind): Exception calling "Bind" with "3" argument(s): "The request failed. The remote server returned an error: (401) Unauthorized." Failed to open source message store ([email protected])

During the token obtain process does the admin account used need to have a license, or delegated permission to the source mailbox? My impression was that the oauth app permission was used, so delegation is not needed.