You have provided a substantial lack of details about how the system is setup, what power configuration you're using, etc.
The first rule of troubleshooting is DETAILS.
So i recently put a carputer in, and it was working perfectly yesterday, i used it about 7 different times yesterday (turning it on and off) and not a problem but i get in my car today and hit the power button and nothing happens, Theres a little green lite on the motherboard that turns on whenever there is power to the mother board and its on, the button is hooked up and everything else is hooked up but it just doesnt seem to want to turn on, i've tried everything i can think off, i tried with a different button. I haven't tried a different power supply but with the lite on the motherboad on, to me that means it has power. If it matters it rained pretty hard last night and also did a little hailin', but i'm 100% positive the computer didn't get wet at all. Thank you for your help
I have a power invertor running from the battery and then just the stock power supply in the computer whichs plugs into the power invertor, the power invertor is working fine because i run other things off of it, its a 700w invertor,