The Doctor gets to work on the machine. He can reroute the system, he can undo it, but the mechanisms are so old, the wiring so corroded, that he isn't sure he can reroute the system. The button might never have worked.

He looks back and sees Morgana fighting. She's buying him time, but they'll overwhelm her if he doesn't hurry.

Concentrate, Doctor.

He pulls out another bunch of wires and starts over.