I did a good sign-up on the site. No problem, easy and fast.
I have also installed MetaTrader 5 on my android device. Just in case I tried to sign-in the DEMO account number first but did not want to connect. The only thing that connects is the MetaQuotes-Demo provide by the app.
I'm not sure if the problem about login already solve, but I was also able to sign up without problem, no cookie refresh or installation of any app, I received the email confirmation via my email fast in less than seconds and now I'm using the Demo via BTC Trading and sees it have demo for USDT trading too. I also try checking different buttons and links that brings me to join the affiliate program.
Hopefully their login problem above is now solved.