First, I would try logging in by accessing the site through official channels, The, I would go to the official IRS website and call them. Amazingly, someone will actually talk to you on the phone! Be patient if they are busy . . . you'll get to talk with them eventually.
The govt requires the Social Security account website users to change the password every 6 months. Since I only check my statement annually, I am locked out every time I want to check it. I call, they reset it and email me the link, and then I'm back in. They are always super polite and patient on the phone . . . I imagine they deal with non-tech saavy grandmas a lot.