1) Is it possible that you are logged in with another computer? (trying to login downstairs with your desktop while your laptop upstairs is logged in). I understand ancestry will only allow one computer at a time in ancestry.
2) Can you login to ancestry.com with your browser? If so, what happens if you copy and paste the ancestry.com url from the browser page where you are logged in to the url line of your Web Search page in FTM?
3) Have you exited FTM and rebooted your machine?
4) Sometimes ancestry's web site simply goes on vacation. What happens the next day?
5) If none of the above works try trouble shooting with a Support person at their phone number tomorrow: 1-800-262-3787