Remote start, reprogram or electrical issue?

Hi, I just went through the lengthy procedure of replacing the hvac box and heater core. When I did that I disconnected the wiring harness and all the modules. So now it’s all back together and the only issue left to resolve is the factory remote start. It’s not working, is there a troubleshooting guide or can someone send me in the right direction. I did a quick search and lots of posts about key fobs etc, this I don’t think, is my issue.

 

You may have tripped the immobilizer. Idk much about it though. You may need to look up the reset procedures to it.