Can't log in

Good morning / afternoon / evening.

A friend of mine recently downloaded this game but is unable to log in. I have tried to log in to her account on my computer, and it actually worked, with no problems. On her computer, however, she is unable to log in. She has minded the general aspects, such as Caps Lock and the likes of it.

Can someone help, please? We really would like to play the game, for it seems to be quite entertaining.

Thank you for your attention.