Can’t add member – GroupMe Review

I’m using this as a way to communicate amongst my group and we have been trying to add another member but keep getting an error message saying “FAILED”. I have checked the internet, blogs, nothing says how to fix this and it’s extremely frustrating!!! She has groupme for different group chats but now she can’t be added into new ones. Fix it!!! Help!! Please ?
Review by Xiomy.xo on GroupMe.