Even if you have never plugged into a computer before, it would still be recognized by one if it was booting and powering normally. You just wouldn’t be able to sync it or backup without being able to enter the password. You can also try putting it into recovery mode to see if it’s recognized. Which would also allow you to try and process an update, if it is in fact a software problem causing it to not boot. This might be tricky if you can’t see the display, it will likely be a bit of a dance with timings, but it would at least tell you the device is responding.
If you took it to the Apple Store and they ran their Integrated Circuit Checker, which is the tool that’s used to see if a device is capable of powering on, those can also give false results (can indicate it’s not capable of turning on, or it’s drawing very little power) if the device is actually on and the screen is locked.
But this still sounds to me, like if a computer is not recognizing the device, it’s probably not software.