Apps purchased in Mac App Store won't download

I'm finding this appears to be more the App Store app is failing to update what we see against what is actually happening. Restarting the App Store app appears to be enough to get a clearer picture of running/pending updates.

Ditto. I've experienced this on iOS. Sometimes turning off WiFi and re-downloading update over carrier (LTE/3G) seems to work. I've noticed however, it's more of a delay when updating the Apps via Appe Store. Attempted to update on my WiFi (5Ghz) and noticed the update stalled. However, waited 5 minnutes and it resumed without issue.

I'm seeing the same problem. Sierra tells me that a particular application, that had been installed via the App Store under El Capitan, is "damaged and can't be opened" and to download it again from the App Store. This, in turn hangs the App Store, and nothing is ever downloaded or installed.