Ran into an annoying issue on my iPhone where I would get an error pressing the “Update All” in the App Store. It would act like it was going to start downloading an app(s) but would never prompt for a password and then fail with a generic error asking if you want to retry. Would also get the same error if I tried updating a single app or reinstalling on of the 10 apps needing an update at the time the error started. I could however download other new apps without issue.
Had a similar issues a while back so I gave that same solution a try and that seemed to correct the problem. Not sure what it is but I seem to be a stone cold iPhone-App-Store-database mangler, iExplorer is a lifesaver.