2005 Cadillac Escalade Esv Starting

Everytime it starts to get cool out the truck wont start. We have replaced the battery as per GM's request. Now here we are a few months later and it won't start again! We have taken it in and we have been told nothing is wrong what could this be? It only seems to do it when it gets a little cold, the vehicle is plugged in when it gets cool so a cold engine is out of the question.