I just got locked out a second ago and had to login on private browsing. Not sure if things on my end are screwed up in my browser or something. I had to go into private browsing to start a fresh session.
Update: I was still logged into other .win sites like wsbets.win so I went there and logged out, then logged back in here at TD. That fixed it.
I just did a restart on my phone, and I was logged back in.