John Deere D105 wont start

I have a D105 that I bought new last summer. I was mowing the yard the other day when I ran into a small stick, maybe 1/4 to 1/2" diameter. Immediately after hitting the stick the engine stopped moving forward. (I would give it gas, but it wouldn't move).

I tried tightening the belt based on the instructions in the owners manual. After tightening I tried to start the engine, but now the engine will not start at all. It turns over, but wont start up.

Any ideas what could be causing this?