Maybe your firewall is what's disallowing the game to connect? Get into your settings and find your firewall, and add FH to the allow list. Do the same for any anitvirus program you may be using that could be blocking FH from the internet.
If it's not your firewall or antivirus, it could be that Cloudflare is down in your area still, which is what allows the game to connect to the server. And with that, you'll just have to wait because there's nothing you can do to fix it, one of the staff is trying to work out the issue as far as I know.
If not those things above, then have you gotten the update for FH yet? The old FH will not work anymore, you need the update in order to play. The update should be available for download on the Download page now, you can use either the web setup or the torrent (will need a program that can download torrents) click where it says "Linux and Mac users look here" below the available downloads. Uninstall your current FH (back up ANY preset or downloaded map files and things you may want to keep), delete the folder once it's uninstalled, then download the update and install it. Once that is all done, try running through the tab login process again and then log into game. You should get through to the server then. Also don't freak out if you see a white screen in the character creator, this is NOT a missing texture! Just the way it was made for the update!
Just to clarify in case you get the other message constantly; if it is your password or username however, I'd note that there is a 16 character limit for both. If your password is above 16 characters long, you can change it by clicking on Forgot Password in that big yellow box at the top of the page to the right, this will direct you to a page where you can reset your password for both the game and the forum, follow the steps to doing so and give it some time for it to take effect, I waited a day but it shouldn't take longer than an hour I think. If it's your username that's over the 16 character limit, well then you're out of luck, because there's no way of correcting that so you'd have to make a new account.
