I’ve had a customer call me on 2 occasions, to fix (amongst other problems) two laptop problems (first was no sound, the second was no network access).
In both cases, the solution obvious (if you know what to look for).
The sound hardware all looked fine, until I realised the laptop had a difficult to see volume dial at the front… just turn the dial, and the sound is back!
The wireless network wasn’t working due to the wireless switch (on the side of the laptop), being in the “off” position.
Luckily I didn’t waste much time looking for a phantom problem, and solved the problems quickly.