How To: Reset your Google account AdWords association
When setting up a Google account to link to a Master Client Center (MCC), if an existing AdWords account is associated with that Google account, it isn’t straightforward to link to a different AdWords account, or MCC.
This issue occurs when you try to set up a new link to a MCC from a Google account that has an existing association with an individual AdWords account.
When you are trying to associate with a MCC on an account with an existing AdWords account linked, it isn’t clear that there is a way to ‘unlink’ the individual AdWords account which may have been created in error during the link process, or there has been an AdWords account used in the past.
To reset an AdWords account to the original “no account” status so that you can link to an MCC, simply:
1) Add another account (set up a throwaway Google account if necessary)
2) set up that user as an administrator,
3) Remove access on the original account that you want to reset.
This will revert your main Google Account to the non-linked state, and it will then be possible to link that account to the MCC.