I see you have carried the below out to some degree however please try again using the method below, if you still have trouble let me know the identity of the kindle ie kindle fire\paperwhite etc and the age>>>
Please reset the kindle by holding down the on/off switch for 40 seconds (use a watch to time) ignore any messages the kindle may display, then release your finger the kindle should reboot and re-load the operating system, you may have to do this both on and off the charger and upto 4 times before it resets.
Let me know if you need more help
A positive rating is appreciated thank you
Do you need any more help with this please?