My iPhone 14 pro max won’t turn on

If you already tried (to no avail) a forced restart of your 14, as per the section "On your iPhone 8 or later, including iPhone SE (2nd and 3rd generation)" in the support article that led you here, 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:--> Apple – Location Selector. 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 "simple" restart (or reboot) can be performed on an iPhone 14, by using these gestures:

1. Press and hold either volume button and the side button until the power-off slider appears.
2. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
3. To turn your device back on, press and hold the side button (on the right side of your iPhone) until you see the Apple logo.

A "forced" restart (or reboot) can be performed on an iPhone 14, by using these gestures:

Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top (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).

In your situation, a "forced" restart is recommended.

Regards

Giulio