I can’t remember for sure, but I think they want a “full” name, meaning more than one name. Unless of course, “Josh” is some famous mononym, like Cher or Sting. This is to identify you to the world, not to your friends.
I can’t remember for sure, but I have a vague memory of someone having this problem and using the full name fixed it. If not, check back.
I also see errors in the console (12) can you look at the Console tab as well? You might be blocking something. Anyway, let us know if the problem persists on your own network.