Anti theft relearn procedure issues

I replaced the ignition cylinder. The new one comes with a set of new keys. Both the new lock cylinder and the keys work fine. The issue seems to be with the anti theft learn procedure, not the key. The engine cranks but dies immediately while the "Security" light flashes three times but does not stay on like the relearn procedure says it should. I bought the lock cylinder (with keys) from carparts.com, which seems to be a credible car part online store hence the reviews the website has. Does the new key have to have the same chip the old key has? I thought the whole point of the relearn procedure was for a new key to be programmed with the truck.

Well, you see the new key IS the problem! .. The security system doesn't recognize it .. Locksmith can make a key with same resistance value chip as the old key had - but it must be cut to work in new lock cylinder. ... Good luck with it!

I understand now. I'll contact a locksmith first thing in the morning. Really appreciate your help!