Status Changing to Pending

I create a WordPress user, and then go to "Add Member" to add a new member manually, so I can give them a free membership to a paid level. When I add the member, it takes me to the screen to choose the membership, so I choose the paid membership. I press save ... I expect that now the user is an active member under the paid level, but instead, when I save it says "pending - waiting billing" ... when I try to switch to Active and save it, it keeps resetting back to pending.