Will not start with key

Is the theft light remaining on? If so then it could be the key however, if the engine was replaced the theft system should not be effected.

If the pump is working but the injectors are not firing then the ECM is preventing them from doing so. This could be a number of items but we need to find out if the theft light is on. If not, have them check for codes. I suspect we have some. If not, we need to check to make sure the crank sensor is connected and installed correctly as well as this is what the ECM looks at to determine firing sequence.

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor