# API: Hosted add-on manifest webhooks not invoking function; ADDON\_CALLBACK\_URL returned

**URL:** <https://community.servicem8.com/t/api-hosted-add-on-manifest-webhooks-not-invoking-function-addon-callback-url-returned/1203>\
**Category:** API & SDK\
**Created:** [September 23, 2026, 1:40am UTC](https://community.servicem8.com/t/api-hosted-add-on-manifest-webhooks-not-invoking-function-addon-callback-url-returned/1203 "2026-09-23T01:40:10Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![christine\_gamboa](https://avatars.discourse-cdn.com/v4/letter/c/898d66/32.png) [@christine\_gamboa](https://community.servicem8.com/u/christine_gamboa)\
**Post date:** [September 23, 2026, 1:40am UTC](https://community.servicem8.com/t/api-hosted-add-on-manifest-webhooks-not-invoking-function-addon-callback-url-returned/1203/1 "2026-09-23T01:40:10Z")

</div>

Our private add-on uses ServiceM8-hosted functions and manifest-declared webhooks. Manual job actions invoke the function, but our controlled attachment update has not produced a webhook invocation.

- Account UUID: e9192883-164e-4253-884b-1b927a71b4bb

- Add-on: Jet Plus Paid Receipt, slug paid-receipt, ID 541175, version 0.4, status Ready
- Latest deployment: 01a0cb8c-1f62-7de9-be11-e135a586a3fb
- Toolkit: official @servicem8/addon-kit 1.3.0
- Test job: JP5676, UUID 01a0c2ae-5935-7de9-be10-8f219a582ecd
- Test receipt attachment: 38d669fa-f2f6-5e99-a9fd-f1038b5eb902

The deployed function’s own OAuth token returned these sanitized subscriptions from GET /webhook\_subscriptions?status=all:

```json  
[  
{“object”:“job”,“fields”:[“payment\_received”,“payment\_received\_stamp”,“total\_invoice\_amount”,“invoice\_date”],“active”:true,“last\_failure\_reason”:null,“callback\_url”:“ADDON\_CALLBACK\_URL”},  
{“object”:“dboAttachment”,“fields”:[“active”,“tags”],“active”:true,“last\_failure\_reason”:null,“callback\_url”:“ADDON\_CALLBACK\_URL”}  
]  
```

During testing on 23 September 2026 (local time), POST /api\_1.0/dboattachment/38d669fa-f2f6-5e99-a9fd-f1038b5eb902.json changed tags to jppr\_webhook\_probe and returned 200. A subsequent read confirmed the value. No webhook log or expected test-only probe Note was observed. Manual action logs were visible, including at 2026-09-22T23:57:28Z.

Please check whether these manifest subscriptions are correctly connected to the hosted function and advise how to restore automatic invocations. Is ADDON\_CALLBACK\_URL expected for a hosted SDK add-on, and can the internal delivery logs explain the missing event? Sending remains restricted to the already-completed test job; please do not replay customer sends as part of diagnosis.

Related ServiceM8 staff guidance: [Is there a timing problem with registering a webhook on addon registration?](https://community.servicem8.com/t/is-there-a-timing-problem-with-registering-a-webhook-on-addon-registration/429)