Try turning off your VPN, proxy or tor-exit node. If you are not comfortable taking these off, then you can simply switch it to a new IP and attempt your registration again. Certain IPs have been abused for various reasons and you get the message you are experiencing. This fee will now be associated with the account and will not go away if you log-in on a new IP. You must re-make your account that is receiving this message or simply pay the 1665 Satoshi.