If your drone takes energy etc from you after every attack and you have no energy to give it won't attack.. This is the most common reason it won't fire I think..

maybe because it requires a certian amount of energy to be fored and you dont have enough, also when you do a double cooldown it doesnt fire and if you are overheated and it requires heat then it doesnt fire (im assuming on that i havent used a heat drone in a very long time) and i dont think i need to explain bullet or rocket ammunition do i?

You're wrong about heat drones, if your mech didn't do double cooldown, these drones fire, even if the heat generation will cause overheat, it just overheats your mech
About all others,(energy,bullets,rockets) though, if you don't have enough of them, it doesn't fire(double cooldown still prohibits it from firing...) and if a drone is using more than one of these, you need to apply these rules for each of them.

lol my bad i havent used a heat drone in a very long time ive been using the blueberry