Hi Daniel,
MxAdmin and password 1 will only work locally.
Have you published your app? If yes, then try login in with demo users as shown in below screenshot. I hope this helps. All the best!
Try changing the Administrator user name from MxAdmin to something else in Studio Pro, and then try to log in using that new user name. Make sure it's something you've not used before. If you have this hosted outside Studio Pro you will need to change it there.
Good luck!