ECU changed

Whoever you have do the programming will need the entire car because not only the keys need to be programmed but a few of the other modules will need to be programmed to the new ECU and the VIN in the replacement ECU will need to be reset to match the VIN of the car. What was the reason for the ECU change?

Programming keys for a 2007 Hyundai Genesis Coupe typically requires specialized equipment and procedures that are often performed by a dealership or a qualified automotive locksmith. While some modern vehicles allow for key programming without bringing the car in, this is not usually the case for older vehicles like the 2007 Hyundai Genesis Coupe.

Both of those are related to the ECU not being coded to the car. They are basically saying that the security system cannot talk to the key and the ECU cannot talk to the immobilizer. That is why you will need a good scan tool that can go in and alter the VIN and then initialize the keys. It may also need the ECU to be updated to make it work properly, that takes a dealer level scan tool with a dealer code.

Here are instructions on how to add keys and changing the ECU in the diagrams below.
Check out the diagrams (below). Please let us know if you need anything else to get the problem fixed.

One item to add to the above guides. You need a scan tool that is capable of doing programing on a Hyundai, the factory tool can do that as can a couple of the aftermarket units but you also need the interface and access to Hyundai's programming software.

https://www.hyundaitechinfo.com/ is the site that you use.

It has a listing under programming that shows which J2534 boxes work to set up the ECU. Once it's set up you can deal with the rest of the systems.