Adding a family: Server error

i am trying to add a family member with her own apple id to my family account.

but whatever I do it returns with this error:

"Cannot Complete Action

Apple ID couldn't be created because of a server error"

it does this with basically anyone I try to add

is this fixable?

I have to note I do run ios8.4 beta on my iphone but the error pops up to on my non beta ipad