5 years ago, my parents got me a Toshiba C655 laptop for Christmas, and in Summer of 2013, it started to have overheating issues. Someone was paid to try to fix it and he was unable to fix it. I was ready to give the parts away to a neighbor who works with computers and such, and I wanted to take a look a the inside to see what was there (nightmare to disassemble by the way)... and I found the issue... TL;DR: Always make sure your stuff is plugged in. Mostly posting this because I honestly found it funny.
If the guy you paid was part of a computer fixing business then he lied to you They have software which detects the issues when they plug the faulty computer into it
The interesting thing was that the motherboard and the hard drive had to be replaced because they failed due to the mass over-heatings, so some hands-on work was done. Also, it was a person who did work for Staples since they don't have their own repair center in store.