Error: INVALID_CHAMP_SELECTION

Just bought a new champ (karma) and have only been able to successfully start a game with her once. I've tried restarting the client, clicking around in my profile under owned champions, and trying to select other champs then re-selecting Karma.

At first she doesn't even show up as a playable champ when I go to team builder. I have to exit and go back in to team builder multiple times before she shows up. When she finally shows and I select the role/spells/lane, I hit "find group" only to get the error message "INVALID_CHAMP_SELECTION." At this point I'm locked out of team builder even if I switch champs or lane. then I can can start over only to be back at the same problem where she doesn't show up.