I have a Galaxy S5 Active and the hotspot has quit working for all of my devices. I keep re-entering the password and the system keeps asking me to resubmit it.
Did you recently update anything on your software, OS updates, security patches? Try wiping the cache on the phone and if that doesn't work make a backup and factory reset to see if it resolves it. It clearly things you are putting in the wrong password or no password at all which would be odd.