Select Allow access to all APIs. The settings on this page should now appear as follows:
Click Save changes.
In the Google Apps control panel, go to Advanced Tools tab > Authentication section,
and click Manage third party OAuth Client access.
Verify that you’ve allowed access to all APIs:
To migrate data into a multi-domain environment:
1. In the Google Apps control panel, go to Advanced Tools > Authentication section and click Manage OAuth domain key.
Preparing for Your Migration