Dead iPad Pro 12.9 (original model).

I have an original iPad Pro 12.9 inch that has worked flawlessly until about a week ago when I unplugged it from charging and I couldn't get it to wake up, or start up... just black screen and no indication of life. The battery was not depleted the last time I used it, and the iPad was plugged in to an Apple charger for the device over night before it wouldn't start up -- checked cables and charging device and they both work fine. The battery seemed to hold a relatively normal charge life before this incident.

Tried all the different things listed online to get it to start up, but no luck. I think I installed the latest iOS version update maybe a week or two earlier and seemed to be working normally before the problem.

Any ideas? Thanks!