Is "Cross the bridge and then enter the tunnel" incorrect? And if so, why? What am I missing?

I wrote "Go into the tunnel after crossing the bridge" must it follow the same other? It's just rearranged 28/10/2017

Why is go into the tunnel not acceptable?? How is this different from "go in the tunnel??????? This is getting frustrating beyond words!!!

This is how you know Duolingo is headquartered in Pittsburgh