My iPhone won't charge or turn on

Put it on charge for at least half an hour, then, keeping it plugged in, try a "forced" restart of your iPhone, using these instructions:

Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the side (power) button. Only when the Apple logo appears (it might take 10-20 seconds), release that button (ignore all other screens that might appear, the one with the "slider" to turn the device off included).

Regards

Giulio