To reiterate, if anyone reading this has discovered that their scheduled reports have stopped running within the past few days, please let me know and I can forward this on to the add-ons team to investigate.
Here's the information you need to send me:
1) A link to the sheet that failed to update.
2) The email address off the owner of the sheet.
3) The date/time of the last known run.
4) The frequency with which scheduled reports are supposed to run.
5) Whether or not the schedule dialog indicates that scheduling is currently enabled.
(Re: #5 above, in some cases scheduled reports fail but the schedule persists, in other cases the schedule gets disassociated with the sheet for some reason. Both of these are known bugs that the add-ons team is currently implementing fixes for)