Try to press the backspace button at the very front of the name and the "Del (delete)" button at the very end of the name
Try this. This happens to me all the time, even though I never add any spaces in the name, sometimes the game likes to add spaces at the beginning/end of the character name. If you can't get it to save, I would suggest re-loading Feralheart (write down the color numbers/items and markings used if you don't want to lose the effort you've put into your character.) Let me know if this helps