Revive in ASD

So a buddy of mine and me played a ASD quest. He died and I tried to revive him with a MedPen, no success. He respawned at the ASD med-wing. Next time one of us died, Med-pistol; also no success, pyro-medical attachment: no revive. We died like 5 times until one of us spawned at PT, the other one in ASD. Are we missing something? Why can’t we revive each other? When do you spawn in ASD and when at your imprint? I’m confused….