Google Transfer Error: "Transfer Your Content is only available to authorized G Suite for Education Accounts" (Public)

When transferring data from your MIX Gmail to a personal Gmail account, you may receive an error that says:

This happens when you are logged into two instances of a Google account in the same web browser window. Google caches a login session, and cannot process the change in the same window.

To fix this error, log into your Google accounts in separate browser instances. If you’re using Chrome, log into one account using your normal browser window and another using an incognito window. You can also log into your accounts using separate web browsers, like Firefox, Microsoft Edge, or Safari.

For more information, view Google’s Transfer Your Content page for instructions.