[GAMEPLAY] Thams ult is not working

I played 5v5 summoners rift game as Tham and I couldn't ult. When I pressed R, he would go into his open mouth channeling stance, but after reactivating the ability it would only cancel it. I tried waiting for an ally to enter and when 1 entered, Tham would just walk to the ult destination with the ally inside like I only used my W. 1 time even when I spit an allied cait out of this "ult" she took about 10% hp damage.