If your on the DTV, the CURRENT understanding is you would need to go and get an extension for 1900 baht. That would get you another 180 days. Additionally you would become a tax resident after 180 total days in the country whether they were consecutive or not.
Bummer, I also first made the mistake of not "signing up/create an account" that's where I first saw this message. Than I created account, they email you a password, then login. I'm sure you have done these things but just wanted share the steps I did. When I did on my phone I got this message and somehow my PC let me in. Hope this helped.