Just to add my name to the list of those experiencing this issue - started early this morning when trying to update a single App (Ebay), never had it before so was a bit of a surprise.
Like others, had a quick look at Apple System Status to see if anything was down (nothing reported - surprise, surprise!) and then tried logging out/in, Authorisation, Reboot etc all to no effect. Discovered like others if you try several times it finally decides to download, also the App Store was taking a long time to appear (20sec or so) - 3Hrs later it is now back to it's fast refresh. It's almost as though Apple are struggling with demand at certain times, a bit like login in to Pokemon GO in the early days!
The "8392" error was also popping up when first opening iTunes even if I did not go straight to the Apps section - that made me think something was trying to check but failing, so I decided to try turning off "Automatic Downloads" for Apps on my iMac, iPhone and iPad and I no longer see that opening error.
3Hrs after first noticing this issue it appears to be getting better (as mentioned above App Store Page now refreshes quickly and just tried clicking to download an App and it started after a long wait (30 secs or so), but got no error message.
I'm going to leave "Automatic Downloads" off at the moment just incase it's a problem with Apple servers not being able to link properly there Mac and iOS systems (always synced via iTunes/cable anyhow) and see how things go, but from what I've noticed over the last few hrs it does appear to be at Apple's end, even if support does not acknowledge so!