Update: As of 3:30 PM ET we are now receiving app updates through the Store on our phone. Other reports are coming in as well confirming the fix.
All morning we have been receiving tips from users via email and Twitter that the Windows Store is no longer reporting app updates to users. Case in point is the new Slack (beta) update, which we reported on earlier, but is not showing for many. The same applies for yesterday's rather critical Insider app update that matters for Lumia 950 and Lumia 950 XL owners.
Windows Central does not yet have enough information on the range of the problem including devices or OS builds (or whether that even matters). The issue is complicated by many users may not even know there is a problem as checking for updates simply returns no hits. However, there is at least one thread in our forums with users discussing the issue and many users in our comments are also experiencing the outage.
The lack of updates is likely due to an error with the Store and configuration rather than the devices themselves. As such, we could see this resolved at any time.
For now, if you no longer see app updates on your phone (or PC) let us know in comments what device and OS and build you are on.