Characters dissapearing

Hi, i have problem with half of my characters. I still have them when i log on but they dont have any name and i am not able to log into game with them.

Could you explain to me why is that? and what can be done to repair this issue?

Thanks. have a nice day

They need to have their names changed. Try entering them, close client if it fails then reopen and try again. It'll ask for a rename eventually.