I cooked potatoes at 375 degrees F for an hour and they were still not cooked. Shouldn’t they be done?

Not necessarily. When I used to do catering activities and had to use someone else’s oven I learned a long time ago that just because the dial says a number doesn’t mean the temperature inside the oven matches. Especially, if it has to be opened multiple times, it’s the temperature at the center of the potato that matters! Buy a metal stem thermometer to take the internal temperature of food and make sure to bake the potatoes to the minimum internal temperature, which is 185 degrees F (it will continue to cook before being served, like how a restaurants use an insert for the line at a buffet) and 210 degrees F to be fully cooked.