Linking Device problems

Platform, device version and operating system

Screenshot or image
In the picture, there would be an email and it’s password so I don’t feel like sharing it, but I promise, on both devices, the emails and passwords are both the same!

What you were expecting to happen, and what actually happened
I wanted to link my GF’s account on a computer, typing exactly the same email and password, expecting it would link, but instead, it said that I wrote either of them wrong.

How often does this happen? When did it begin happening?
Every single time I tried linking the account, the same happened.

Steps to make it happen again
Open Settings, tap Account Tab, tap Link to Another Account, write the RIGHT email and password, tap Submit.