Obviously First if you haven't done so restart your game, Secondly If that doesn't work try going into versions and creating a new profile, If that doesn't work then if you are using something that use's mod then there is a possibility that is causing your game not to work. Do you get the same problem on other server's or royalcraft exclusively?
I get this a lot after logging an account onto a server with a thing called, "Console Client". If you're using that, you gotta restart your game. Secondly, I also found you can fix this by logging into a different account, joining a server with it, log out of it, then load your account back up. Please do reply to me if this works. I can try and assist you more via a discord call, add me if needed. XenZ#1582