Man. I got a cheap PS1 recently and it.. almost works. It's in pristine condition but it doesn't always boot right. So I took it to the phone repair shop down the street and had the guy take a look at it, and after pressing it a bit in a few places, it started booting perfectly every time. But now after getting it back home and putting it back together, it's back to not working. I don't even need it to work, I already have a PSOne, but at this point I just want it to work for the sake of it. It's in beautiful condition so it's such a shame to see it not working right...

@Pink_Hat: it’s probably going to take some trial and error.

Try starting it with a CD in it and then without (try a different disc)
Try starting it while it’s lifted at an angle
Try cleaning the optical lens with the right solution
Try pressing those buttons again?
Other than that you could try looking into this
https://www.ifixit.com/Wiki/PlayStation_Troubleshooting