Some folks have had success by shutting down TTX.
1) then deleting all cookies. and trying again.
or
2) Shutting down TTX and rebooting computer...and trying agin.
or
3) With TTX shut down...
....3a) in a browser, login, then log out of the account you don't want (just to make sure it's logged off).
....3b) in a browser again, log into the account you do want.....and leave it open
.....3c) restart TTX and attempt the import again.
One of those should work
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*