The newer iPads with the USB-C charge ports are finicky little things. We have so many customers send in iPads because the "won't charge" - only to find that they are perfectly fine if you have the right cable and charging block.

This kit includes our tried and true favorites:
Anker 20W USBC charger
Anker USBC-to-USBC cable (3ft - color may vary)
and a USBC ammeter/tester 

The tester actually measures quite a lot of things, but when the iPad is plugged in through this tester, the green numbers will show whether the iPad is charging. You're looking for a number around 2.35 if the iPad hasn't been charged in a while