If you tried linking your accounts but it seems not to have worked, please unlink and relink your account - there may have been a mix-up with your credentials.
To unlink your account, navigate to the profile icon in the header of the main page and click Mechanical Turk Account from the profile dropdown menu. On the next page, click on Delete MTurk Settings. To relink your accounts enter your Access Key ID and Secret Access Key. For more information on the steps needed to link accounts, please refer to the Linking MTurk and TurkPrime Accounts Users' Guide.