@EricNewman
I could not authenticate. It seems launcher can’t accept too long passwords. My password was 20 characters long (using a password generator), I used it fine on website, but in launcher it did not work. I shortened password and it now works fine.
solution is either for user to shorten their password or for Epic to fix this in launcher. My opinion is it should be fixed in launcher, because if password is accepted on website it should not give user any problems after install.