1993 Camaro wont start

Just bought 1993 camaro 2 wks ago. Its has 147,460 miles on 3.4 v6. Its automatic has no sounds and no leaks. Took to mechanic to look over he replaced water pump, serpentine belt and flushed fluids. He said starting system in great condition and car overall in good conditon. Got it home, used it a few times the next morning. Went to start it and nothing. Everything works but it wont turn over. Like something just cut the power to the ignition only. Towed it to the mechanics they took out the aftermarket alarm system but it wasnt that. They checked the key wasnt that. Its going on the 3rd day and their puzzled. Please if you can help I would appreciate it. Thank you.