Some of my iPhone or iPad keys or screen taps do not work - is my screen faulty?
How to diagnose patchy iPhone screen.
If you find that when typing, one or two keys do not work, or some screen taps do nothing, it is possible that part of the screen is unresponsive.
First thing to try is turn the screen to Landscape mode. Do the keys work now?
If the same keys do not work then it is probably software so try a Forced restart
Force restart iPhone – Apple Support (UK)
If however those keys now work in Landscape then there is a good chance that part of the screen is unresponsive to touch.
Here is a simple test to try and find "bare patches"
Open a Note in the Notes App
Tap on the Markup Pencil icon
Select a broad tip with a dark color
Scribble lines all over the screen
If the suspect part of the keyboard or screen is near the bottom you may have to do the test again but in landscape (both ways round)
If you see a bare patch then there is a good chance that part of the screen is faulty in which case you should arrange a repair iPhone Repair - Official Apple Support
or Contact - Official Apple Support
Anything other than Screen or Battery may be a replacement phone and the price is in the article under "Other damage"
See also: Get your iPhone, iPad, or iPod touch ready for service - Apple Support
Other official advice here
If the screen isn't working on your iPhone or iPad – Apple Support (UK)