Why was Pittsburgh not granted the third challenge?

Well, I was watching the Steelers-Ravens game on CBS and Phil Simms and the other announcer kept saying that Pittsburgh didn't have any more Challenges. I was confused because the Steelers won their first challenge on the kickoff. He should've gotten a third since he won his first. I don't know if Simms and the whole crew was stupid or if Tomlin just didn't want to use it?