I never understood the rational for having to energize it to cool, as Doug said, the default operating condition is cool. It's been like that on my marine units since I can remember and even when Dometic bought Marine Air and Cruisair, that stayed the same.
If it is a new unit, I would look at getting the dealer to replace it under warranty. The usual cause of a sticking solenoid is a small piece of trash or debris that was introduced into the system when it was built. The valve operates by teflon slides moving from one side to the other and it doesn't take much to hang it up. Not common, but it does happen, and it's likely it will stick on you again. Replacing the reversing valve is labor intensive and requires a moderate amount of skill and experience to do it without burning it up with the torch and most shops are not going to want to do it. I've been changing them for 15 years and my pucker factor still goes up when I have to do one on my marine units.
You can give the valve a light tap on the end with a wooden stick if it sticks again, but noting heavier.
If it is a heat pump, the reversing valve solenoid has to energize for it to run in cool mode. You either have a stuck reversing valve, a defective reversing valve solenoid, or the control board for the unit is defective and not causing the solenoid to energize. It's an easy diagnosis for someone familiar with these units, or you can wait and get every kind of armchair diagnosis here and then take it to a shop.
It is just amazing how so many of these simple questions turn into a pissing match about who is smarter.
And the end result is that after 4 pages of comments, the furnace still works on propane and 12VDC, either from the converter or the battery.
These tech threads just keep getting better and better.
One of the things that amaze me about these electrical threads is that someone hasn't been killed following some of the advice given on here.
Another amazing thing is how many people give advice on wire size and don't even know that wire size for AC and DC are figured differently. I guess it really doesn't matter here as long as everyone gets to post something.