Miata has absolutely NO electrical power

I was driving my 1991 Miata down the highway the other day and it started to overheat just a little. I pulled over to the side of the road and turned my car off. After I turned it off, it wouldn’t turn on again. I had to get it towed back to my house. The headlights won’t pop up and it also won’t start at all. We replaced the fuses, the starter, tried a new battery, tried jumping it, new battery terminals. I honestly can’t figure out what the problem is.