After replacing the starter, the engine cranks but does not start and the security light flashes?

I changed the starter out and went to crank it and all I get is turn over no start, it's now stuck in security mode. I'm guessing it's stuck in theft mode and that's not allowing it to start. I've looked up and tried almost everything imaginable. I cannot get the security light to stop flashing or turn off whichever. I've been going at this now for months. I'm at a standstill, if you could help me figure this out that would be great. I need to bypass the security system or something.