Can’t connect Kindle Paperwhite

Have you tried a solution offered in If Personal Hotspot is not working on your iPhone or iPad (Wi-Fi + Cellular) - Apple Support

This document has a tip which is to activate a choice in Settings > Personal Hotspot

A little down this page is the option "Maximise Compatibility" and touch on the switch to active this choice. Your Kindle then should connect to your iPhone.

Try another device on the hotspot like a laptop or ipad.

If they work then it's the Kindle that has a compatibility problem.

If they don't work then your Hotspot has a problem - first contact uyour SIM provider to see if you are authorised to tether.