A 2018 11” iPad Pro was left on a charger overnight. The next morning the charge had not increased from the 4% it started at. The iPad would not even connect to a Mac. Tried a different charger to no avail. By then, the charge had reduced to 3%. Argosy West in Prescott said that the iPad was a sealed unit and only Apple could do any repairs, which might come to $350.
Thinking that the best thing to do was destroy it, the iPad was erased and was ready to toss in the trash. On a hunch, it was connected to power again. After less than an hour it was charged to 15%. An hour later, it had charged to over 90%. The iPad was successfully restored from an iPhone backup via iCloud (which took a few hours).
By erasing the iPad, it is guessed that the system settings were cleared enabling the iPad to again take a charge.
John R. Carter, Sr.