I just tested on my iPad. I see the same thing. You could report this problem to the member support team.
I would recommend you use the analysis board on the website to enter the game. Then you can save it to your personal library.
https://support.chess.com/article/1987-how-do-i-use-the-chess-com-library
My son and I played an OTB game and recorded the moves. We then input the game into the App on my iPad for review using Learn > Analysis. The game play through correctly all the way through finish. At the bottom of the screen is the 3hash lines and the SHARE option comes up, but then it doesn’t do anything else.
Is this a bug and I should just move on? Or is this intentional that you cannot create PGNs using the App?