iPhone 14 pro will not start up. Have tried combinations of volume and side buttons. Nothing happens

Do the following EXACTLY as I suggest:

1. Press and quickly release the volume up button
2. Then immediately press and quickly release the volume down button
3. Then immediately press and KEEP HOLDING the side power button. Keep holding it until the Apple Logo appears. It can take a while, so don't let go until you see the Apple Logo. Once you see the Logo, let go and your phone should restart

You should just have to hold the power button if that doesn’t work then take it to the apple store