The site is based on vBulletin.
Then you can't login with the Username and Password properties of THTTPSend.
Those are for website where you can pass username and password via the socket.
Like
https://myuser:password@mydomain.comYou need to look at the way the login is implemented. For example, you can look in Chrome, with F12 developer tools, what is actually posted during a login. If the login is relatively simple, like just passing username and password in a form, then it's simple. If it has a more sophisticated login, like Google and Facebook, then login in will be much harder.
If I look at a vBulletin site it does do a post with username=aaaaaaa&password=bbbbbbbb&privacyconsent=1&securitytoken=guest form-data to /auth/ajax-login, but I'm not sure if that's the only data it sends.