I had updated some other apps earlier this morning (getting ready for AC update). When AC showed up,it was pending. Used the troubleshooter which reset the MS store, cleared the cache, and still pending. My other computer updated without any problems.
Hmmmmmm. Have you tried deleting it from the queue of pending updates ? (From memory there is a "pause" symbol and an X against each update.)
The X should delete it. You can then "get updates" and it should reappear and download. (Hopefully !)
Regards
Harcourt