The main causes I've had with my bike when it refuses to start is either fuel pump issues, fuel hosing issues or carburator issues (needed cleaning).

When the starter is running, you should feel the fuel pump working slowly (like one vibration every second or every other second). If not, your fuel pump is probably toast (very common error).

But as hamlin6 said, please share the whole backstory. It's hard to backtrack what potential damage the theft has left on the bike.