We're excited to announce that we've fully migrated the Xbox Forums to their new home, here on the Microsoft Community forums!
As of today, going to forums.xbox.com will redirect you here to the Xbox area of the Community forums. We've moved all of your existing threads over so you can continue and start conversations with the new forums experience.
We sincerely appreciate the feedback you have provided over this transition and can't wait for you to check out the new Xbox Forums!
Where did you exactly change your gamertag at? It normally takes about 3 days for everything to be switched over and for it to update. You can try to clear your systems cache to see if that will help, but I would wait 3 days before trying to troubleshoot
the issue. :-)