Walk-in fridge problems

Hoping someone might have some thoughts since my repair tech seems to be stumped. Walk in fridge started fluctuating wildly a few days ago. The repair tech said that there is power to the compressor but it isn’t turning on. He says he’s never seen anything like it in 20 years. Any help is appreciated. Located in Las Vegas, it has been very hot (average high around 110) here for the last few weeks.