Just encountered a frustrating problem when updating Numbers in the Mac App Store. There’s “an error has occurred” message in the Updates list as well as Purchased app list for Numbers after a seemingly success but actual fail update. Then, opening Numbers app will fail, showing an alert that the app is still updating. Go back to the MAS, the button for Numbers is now installed, so you cannot update/install the app ever again because App Store deems it alright.
Try deleting the Numbers.app in Application folder won’t help either. The “an error has occurred” is still there and the app status is always “installed” even the app is absent from my Mac. Logging out, and logging in to MAS several times, an error always occurred.
Now googling hundreds of pages. Try the interesting MAS debug mode solutions here, but the problem remains. Try the reset errors solution, still no hope. Even try the reset everything for app store cache solution and safari cache solution, both fails. And nothing going wrong for MAS in the Console even strongly suggested that it might be a MAS server problem, which would requires a bug report eventually. I supposed.
Finally, a non-sense post in somewhere in the piles of discussion threads on the web I’ve browsed gave a helpless cue and last resort action: changing the system language/location to English. The mysterious MAS problem is solved. The latest Numbers update showed and installed.
Now I advocate that a fallback App installer/updater mechanism should be there just in case that MAS goes wrong.