try using the start.bat file.
Some people have the same problem, for example myself,
my account doesn't work when running remnant.exe, but it works when using the start.bat file.
If you still can't login, try making an new account and try it again with both programms (remnant.exe and start.bat)
If you still have any problems contact the higher people like GM's or Admins.
I think they can help you out more if it doesn't work for you after trying this.