CS.RIN.RU has aggressive anti-spam measures. If you are using a high-traffic VPN IP, the server may silently drop the session data to prevent bot accounts, resulting in the "Can't agree" loop.
Practical example
CS RIN is under constant attack from bots, scrapers, and automated spam accounts. Because the forum hosts valuable technical data (including tools for bypassing copy protection for legal backup purposes), it is a high-value target. The "Can't agree to terms" error is a deliberate, albeit poorly named, honeypot trap. It activates when the server suspects your registration request is not coming from a genuine, human user at a standard home IP address. cs rin can%27t agree to terms