Even with billing enabled, if your daily budget is at 0, you will have the same problem. Can you confirm if the daily budget is setup to a number and not fully filled?
The dashboard won't show errors if the problem is billing-related -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To unsubscribe from this group and stop receiving emails from it, send an email to google-appengine+unsubscr...@googlegroups.com. To post to this group, send email to google-appengine@googlegroups.com. Visit this group at http://groups.google.com/group/google-appengine. To view this discussion on the web visit https://groups.google.com/d/msgid/google-appengine/614e889f-88aa-40eb-a179-e92711c59d4c%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.