So, I wanted to mess around in the practice tool while I waited for a pizza delivery since I didn't want to AFK. I decided to play some Shadowfire Kindred. I create the game, lock in my champion, and the fun begins. After 12 attempts to reconnect to the game, I gave up. I decide to try it with a custom game. Set it up, lock in Shadowfire Kindred, boom. Doesn't let me connect to that either.
Figured there must be an error on your end since I haven't had any issues prior, but who knows.