Phone does not power on

if it was me then I would try Force restart iPhone - Apple Support

it if it did not help then I would try Restore your iPhone, iPad, or iPod to factory settings - Apple Support - Apple Support if that did not resolve it then I would

contact apple about repair Contact - Official Apple Support

Perform a Forced Restart on the phone. Follow the instructions very carefully, as this is a bit tricky. You may need to repeat this several times.

Force restart iPhone - Apple Support

There are only 2 possible results when you perform a Forced Restart:

1) The phone returns to normal operation

or

2) There is a hardware problem with the phone that will need attention at the Apple Store (make an appointment) or at an authorized Apple Service shop

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