Problems with family member being added to family premium!

[Anettea]

Hi!

A couple of days ago I upgraded my account from regular premium to family premium, and invited three of my family members. 2 of them registered as premium quickly and successfully, however: my mother´s account had a problem with the registration. When we press the "accept invitation" button in her email, it redirects us to her spotify home page - but without the form she´s supposed to fill in - we´re met only by a black, empty page.

The last couple of days we have tried to resend her invitation almost daily, but with no luck.
Does anyone know what might be wrong or have any suggestion as to what we can do to fix our problem?