Happened a few times now so I think this is a design bug.
If my opponent is overheated when he starts his round, it is automatically cooled. That's ok. If he is overheated even more, he needs to cool all his rounds. Also ok.
But if he has an Energy-Only drone (not a heat generating one) out in the game, it should fire nevertheless. But it does not fire. Even if the opponent has full energy because it is cooling all the time.
If your mech is forced to overheat twice in one round, then you miss out on that turn. This includes the use of your drone for that turn. If you want your drone to fire, make sure you're not being forced to cooldown twice in one round (as well as the obvious having enough Energy-Bullets-Rockets if required).