New user can't add cloud devices

I just purchased a 3TB Mycloud as a personal cloud for my famliy and I recently tried to add my brother’s account. Well, I can add the account, he gets the verification mail and he can login to wd2go.com.
As soon as he tries to add his cloud devices (Windows 8 PC, Windows 7 Laptop, Android Smartphone) and tries to access via the desktop client or app, he is asked to log in with his username (not his email-adress!) which never works.

2 Other accounts are running perfectly, I can add PC devices and a Windows Phone, iPads, iPhones - as well as the second account. I have already tried to make a second account for him (with another email-adress, just to make sure) and it is not working on any of his devices as he can’t login with his username.

We tried this in our local network today. The WDMC is being recognized by any device, he just can’t log in. Manually connecting to the drive works, as he is asked for his email-adress / passwort, not his username / password.

Any ideas?

andieymi wrote:

As soon as he tries to add his cloud devices…and tries to access via the desktop client or app, he is asked to log in with his username (not his email-adress!) which never works.

Have him send you a screenshot of what he’s seeing.

I have never been asked for a USERNAME with the desktop client app – it only asks either for an E-Mail / Password, or a Media Access Code, as shown here: