iPhone 11 Pro won’t turn on

Battery? Other internal component?... but we, just users like you, cannot diagnose that issue remotely, sorry.

If you already tried (to no avail) all the steps provided in the support article that led you here AND you have profermed a Forced restart, as per these instructions:--> Force restart iPhone – Apple Support , I suggest that you make an appointment (*) and have your device inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> https://locate.apple.com/choose-country-region . After checking it out, they'll give you all the available options.

Regards

Giulio

(*) You can do it:

• Online:--> Genius Bar Reservation and Apple Support Options - Apple;
• Contacting a local Apple Store or AASP among the list provided above;
• Using the "Apple Store" app, available and downloadable from AppStore.

A forced restart is a bit tricky procedure, but it's a matter of correct gestures (and a bit of patience):

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).

Giulio

My daughter had this problem recently with the same phone. She tried this specific technique suggested by ProustGiulio and it didn't work. When she took it to a Verizon store, they did the same thing and it worked.

Force restart iPhone - Apple Support