Events are accepted by Azure Event Grid but are not entering subscription matching/delivery

Question

Events are accepted by Azure Event Grid but are not entering subscription matching/delivery

Jamie Bartz 20

Events are still being successfully published to namespace topic <READACTED> (HTTP 200, SuccessfulPublishedEvents > 0 daily)
Since Apr 30, MatchedEventCount dropped to 0 and stayed at 0.
UnmatchedEventCount, DroppedEventCount, and DeadLetteredCount are also 0 in that same period.
Namespace and topic are in Succeeded state, and no relevant config changes were made around the failure window.

Anastasiya Neverova 0 Reputation points

2026-05-06T17:37:00.6066667+00:00

Hi,

Please find the details below:

Filters:
No filters were changed around April 30. We checked the activity logs for that period and did not find any configuration changes. We also verified the event type, subject, and payload structure, and we do not see any changes there.

Additionally, we created a new test subscription without any filters to exclude a filtering issue, but it still did not receive any events.

Diagnostic logs / retries:

We checked the available diagnostic logs and dead-lettering. We saw that there had previously been a large number of both failed received events and successful received events. However, we have a retry policy and dead-lettering configured, and there are not many events in dead-letter storage, so it seems that after some retries the events were eventually received successfully.

However, as shown in the diagram, after April 29 both successful received events and failed received events dropped to 0, while published events still continue to exist.

Webhook / endpoint responses:

For the new webhook test subscription, the endpoint validation succeeds. The webhook responds successfully to the validation request with: WebHook-Allowed-Origin: eventgrid.azure.net

We do not see POST requests reaching the webhook for the actual events, so there are no non-2xx responses from the webhook for those events.

Connectivity / endpoint validation:

Yes, we tested connectivity and endpoint validation after the issue began. We created a new webhook subscription with no filters. The subscription was created successfully and has provisioningState = Succeeded, but it still does not receive events.
Pravallika KV 18,850 Reputation points Microsoft External Staff Moderator

2026-05-07T08:39:34.5433333+00:00

Hi @Anastasiya Neverova , thanks for sharing the details. I have shared the analysis and the resolution over private message. Please check and let us know if you have any questions.

Answer accepted by question author

Pravallika KV 18,850 Microsoft External Staff Moderator

Hi @Jamie Bartz ,

Thanks for the confirmation, glad the issue is resolved.

This is a known issue. We have engaged our backend team to investigate and resolve the issue.

A restart has been done on the stuck app which mitigated the issue and event delivery to the event subscriptions has been restored. A fix is being concurrently deployed to all prod regions, ETA for full deployment is 05/14/2026.

Hope this helps!

If the resolution was helpful, kindly take a moment to click on User's image and click on Yes for was this answer helpful. And, if you have any further query do let us know.

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Your answer

Anastasiya Neverova 0 Reputation points

2026-05-06T17:37:00.6066667+00:00

Hi,

Please find the details below:

Filters:
No filters were changed around April 30. We checked the activity logs for that period and did not find any configuration changes. We also verified the event type, subject, and payload structure, and we do not see any changes there.

Additionally, we created a new test subscription without any filters to exclude a filtering issue, but it still did not receive any events.

Diagnostic logs / retries:

We checked the available diagnostic logs and dead-lettering. We saw that there had previously been a large number of both failed received events and successful received events. However, we have a retry policy and dead-lettering configured, and there are not many events in dead-letter storage, so it seems that after some retries the events were eventually received successfully.

However, as shown in the diagram, after April 29 both successful received events and failed received events dropped to 0, while published events still continue to exist.

Webhook / endpoint responses:

For the new webhook test subscription, the endpoint validation succeeds. The webhook responds successfully to the validation request with: WebHook-Allowed-Origin: eventgrid.azure.net

We do not see POST requests reaching the webhook for the actual events, so there are no non-2xx responses from the webhook for those events.

Connectivity / endpoint validation:

Yes, we tested connectivity and endpoint validation after the issue began. We created a new webhook subscription with no filters. The subscription was created successfully and has provisioningState = Succeeded, but it still does not receive events.
Pravallika KV 18,850 Reputation points Microsoft External Staff Moderator

2026-05-07T08:39:34.5433333+00:00

Hi @Anastasiya Neverova , thanks for sharing the details. I have shared the analysis and the resolution over private message. Please check and let us know if you have any questions.

Answer 1

Vinodh247-1375 44,556 Volunteer Moderator

Hi ,

Thanks for reaching out to Microsoft Q&A.

This is a classic filtering or subscription evaluation issue in Azure Event Grid, not a publishing problem.

Since events are accepted (HTTP 200) but MatchedEventCount - 0 with no unmatched/dropped/dead-lettered events, it strongly indicates that event subscriptions are not matching the incoming events at all. The most likely causes are: a change in event schema or payload structure, subject or event type no longer matching subscription filters, or advanced filters (string/array/numeric) silently filtering everything out. Even small changes (case sensitivity, property path differences, or missing fields) can break matching completely.

Focus on validating one sample event against the subscription filters. Check eventType, subject, and data fields versus the subscription’s filter definition. Also verify if schema version or custom topic format changed upstream around April 30. If nothing obvious, recreate a test subscription with no filters to confirm events flow, then reintroduce filters incrementally.

Please 'Upvote'(Thumbs-up) and 'Accept' as answer if the reply was helpful. This will be benefitting other community members who face the same issue.

Anastasiya Neverova 0 Reputation points

2026-05-06T17:19:58.4266667+00:00

Hi,

Thank you for the response.

We already checked the subscription filters and verified that nothing was changed around the time when the issue started. We also checked the event type, subject, and payload structure, and we do not see any changes there.

Additionally, to exclude a filtering issue, we created a new test subscription without any filters. The subscription was created successfully, but it still did not receive any events.

So at this point, it does not look like a filter mismatch or subscription filter configuration issue. Events are being successfully published to the Event Grid Namespace topic, but they are not being delivered to subscribers, even when the subscription has no filters configured.

Could you please advise what else could cause events to be accepted/published but not delivered or matched by any subscription, including a newly created subscription without filters?