Google Adwords gives the error message " This Google AdWords account is already connected to Marketo and can only be used once. Revoke access in your Google account settings and try again"
1. Click on the Gear Menu in Adwords and Click on "Account Access" tab under account settings.
2. Under Actions menu, Select "Edit Google accounts info" for the Adwords user credentials used in Marketo
3. That will bring up a separate page - myaccount.google.com.
4. In the "Sign-in & security" page there's a "Connected apps & sites" section that lists all of the apps connected to the account - one of them should be Marketo.
5. Clicking the "Manage Apps" link should bring up a list of apps, and clicking on the Marketo app should give you the option to Remove.
6. Once removed, you should be able to reauthorize the account in Marketo.