Teferi, Master of Time Ultimate gave no extra turns.
While at 10 loyalty I used Teferi's ultimate which should have resulted in me getting two extra turns. Instead I received none.
I'm on PC.
I was playing in a cube game.
My opponent was able to take the next turn.
I don't know if this is relevant however after the ultimate was used I played a stone coil serpent for 8 and my opponent used a pact of negation. This ended the turn and then he got his turn.