We built a little over a hundred automated Microsoft Flows connected to Dynamics 365 Online. Many were triggered by simple Create, Update events from Dynamics 365 records.
Microsoft Flows were working just fine for more than a year, then the Client Secret of Service Principal Name is coming to its expiration date. We had it in our calendar to generate a new Client Secret in time to avoid any downtime. New one was configured, more than a hundred Flows remain On, no error was found, and neither any error notification received.
Days and weeks passed by, users started noticing things are missing and the system are not behaving the way it should. Guess what, some Flows just magically stopped working, thanks to 'reliable' Flow management and monitoring system.
We tracked down to the individual Flows. There is Warning about a 'potential problem' as we open it. It has not been triggered in the last 28 days, when it is expected to run at least once a week.
What was causing the problem? It was a million dollars question. There was no obvious link on how to find out what the cause was.
After clicking through many places, eventually I found it. It was under 'Failed checks' filter in the All runs page.
Upon clicking into it, we got error message (why is the first letter of each words capitalised?):
Entity 'callbackregistration' With Id = xxxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxx Does Not Exist
What does it mean? My bet is Microsoft messed it up with the Flow event registration when new Client Secret was updated. The worst part of this is no error notification, all Flows look just fine with status = On.
Simply restarting the Flow triggers the event registration with the host server, and Flow is back to operational as usual.
Lesson learned that it is best to restart all of the Flows after updating the Connection Reference.
At least there is one useful thing I found this time and that is the Failed Check. When building the Flow, and it is not executing when you think it should. The Failed Check section shows the list of missed execution.
Good thing is we can see the detailed error message why it was not executing. This time not every first letter is capitalised. Below is an error by another bug in Flow update.
That's it for now.
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