[Help] - iPhone 12 (iOS 18) - Shut it down to restart it and now it won't turn back on again. Volume button was damaged before, can't force restart. Computer doesn't detect it

As described in the title, I was using the phone last night, needed to restart it, and turned it off. It hasn't turned back on since, even after letting it "rest" the whole night.

I've tried connecting it to the computer to restore, and the computer doesn't detect it. As one of the volume buttons wasn't already working before this, I can't force restart, am I straight out of luck here?

I'm comfortable opening up, I've done repairs before (I changed the battery and screen on this particular iPhone a couple of months ago and it has been working great, apart from the volume button that was already dead before that).

Thanks!