Nothing works on key backyard infinity spa.? When I turn on power I get a nought display instead...

When I turn on power I get a nought display instead of temp on top display. The pump does not come on and I imagine the oven does not come on.
I also cannot turn the light on. I call tech assist and they said it might be a pressure switch adjustment or a bad control board. A up to date board costs 650. Will a bad pressure switch adjustment create all these things to ensue or is it something else.