I have a possible solution.
I had this from the first time I tried to log in after registering. I went through every step of the setup process multiple times to rule out potential errors and checked the realmlist multiple times, too. I tried to register again with the same username and email, and comfirmed that they were taken, meaning that I had entered them correctly. I tried password retrieval and changing my password multiple times, each time attempting to log in with the new password I made, with no success.
Finally I tried the password reset one more time, and used the reset password I was sent to log in to the game, without trying to change it... And it worked. I got in. There must be some sort of bug preventing users from changing their password from the server's random recovery passwords.
I added a text file titled 'password' into the game folder and copy pasted the randomized password there so I wouldn't have to get it from my email everytime.
I hope this helps everyone. Good luck! :)
