iPad pro 10.5-inch not charging nor detecting anything connected lightning connector

I have an issue with my couple fo years old iPad. First, it stopped charging while battery was almost empty. I managed to get it back alive by heating the device (battery voltage went obviously slightly up to enable device to boot up). Then I connected original charger that I got with the iPad - no reaction, nothing. Then, I connected my other iPad's charger (USB-C with Apple USB C - lightening cable), got a pop up about unsupported accessory, unplug and plug it again in finally charging started! However, next day charging even with that USB C charger did not work but I was able to start up the device as there were still proper charge in the battery from previous charge. Connected the iPad to my iMac --> no reaction (neither in the iMac nor in the iPad), then tried with original charger/cable --> no reaction. Did settings and network resets, home key/power key reset etc. nothing. Now with USB C charger, the device switches off (but won't charge) briefly after the cable is plugged. Won't start unless the cable is unplugged again. Then when I boot up the device (w/o charger connected to it), battery symbol shows an empty battery icon, percentage not shown - turned "show percentage" on/off several times under battery in the settings, no percentage e shown, just "empty" battery icon. iPadOS version is the latest available 14.2.

Any idea how to get the iPad fixed? I searched the internet for similar symptoms but could not really find anything fully matching...