How can I tell if my OAuth settings are entered correctly?
In the control panel, go to Advanced Tools -> Manage API client access to view your authorized API clients.
An incorrect entry will include just a URL, in black text, with no explanation, like the first URL (https://apps-apis.google.com/a/feeds/migration) in the image below:
A correct entry will include the name and description of the API in black text, along with the URL in grey text afterward. For example, the image below shows what the same API access looks like when entered properly.
Verifying your configuration and users list
If you’re unable to start a migration or you find that some users were not migrated, there might be an issue with your configuration or users list. To identify and resolve the issue, you can run pre-migration diagnostic tests. These tests can identify errors in connectivity, authentication, and your user list, such as the following
Users in your user list can’t be found on your Microsoft
Exchange or IMAP server
Google Apps Migration for Microsoft
Exchange Administration Guide