After I used my apple pencil last night, I put it along side with my iPad Pro. I did not return the pencil back to its charging position.
Just a moment ago, when I pick up the pencil and try to make it work with the iPad Pro again, the iPad Pro is simply not responding to any pencil move. I tried many different ways: drawing the pencil in vertical or horizontally across the screen, randomly scribble, the "swipe up from lower right corner" move to trigger screen capture, and tapping on the pencil itself. None of this can reconnect the pencil to the iPad Pro.
When I return the pencil to its charging position, iPad reports that it still holds 70% of charge. So it is not a 'flat battery' issue.
So what is the proper way to reconnect apple Pencil 2 to an iPad Pro?