Inviting Realm Issue

When trying to invite my friend to my realm, I got an error in red text saying "Could not invite the provided name"

What I expected to happen was...:
My friend would be invited to the realm.

What actually happened was...:
He was not invited. I received a error reading "Could not invite the provided name"

Steps to Reproduce:
1. Uninvite a friend
2. Invite him back
3. Receive error