SharePoint Online list webhooks not always firing

Occasional Contributor

I am using SharePoint webhooks to pick up document added events (in SharePoint Online). The process is relatively straightfoward and it works well except for one issue.


I have one site collection, with a dozen subsites and up to 5 libraries in each subsite (we're still in testing mode). I have one program with a subscription to all of the libraries.


Every now and then, it seems that SharePoint stops processing events on a particular library. Events continue to fire for other libraries but not this one. In most cases, documents had earlier been added to the library, with successful events raised, but subsequent documents don't raise an event.


The target of the webhook is a Flow, which is relatively unusual, as far as I can see, but aside from this one issue, it works perfectly. Because we are still in testing, transaction rates are very low - in the 6 an hour range or lower.


Has anyone else encountered issues with reluctant events?

3 Replies
Facing this issue right now while working on a similar solution for documents. No explanation I can find.
Have same issue with Lists, change events are not firing, trying to research a way to troubleshoot this.
In my case, it seemed the issue was related to that face that I was not sending a response back to SP on receipt of an event. In my code, I was only sending back a response to the validation request message.

The MS docs don't specifically say that you should send an empty 200 response to the event message, but it seems that if you don't send a response, MS will assume your webhook is no longer active.