Human Agent Advanced Access Required for Facebook Messenger — Meta Error 100 / Subcode 2018276

Hi Zernio Support,

We have completed live testing of the Facebook Messenger Human Agent flow through Zernio and confirmed that the request format is correct.

We are sending messages using:

messagingType = MESSAGE_TAG
messageTag = HUMAN_AGENT

However, Meta consistently rejects the request with:

HTTP 400
Meta error code: 100
Error subcode: 2018276

Meta trace ID:

A9Z1ba1knaCQME4vWcrrWav

The affected Zernio Messenger accounts are:

• 6a75f3e9d0fe733d1a07591d

• 6a91715d77555aae014d186b — existing LSK Tools connection

The Page tokens are healthy and already have pages_messaging. Our testing indicates that the remaining blocker is that the Meta App used by Zernio for these Messenger connections has not been approved for the Human Agent feature / Advanced Access.

Could you please confirm:

1. Which Meta App is currently backing these two Messenger connections?

2. Does that Meta App already have Human Agent Advanced Access approved in Meta App Review?

3. If not, could Zernio submit the Human Agent feature for App Review?

4. After approval, will existing connected Facebook Pages need to be disconnected and re-authorized?

5. Are both account IDs above using the same production Meta App, or different Meta Apps?

Our use case is strictly manual human support in the Zernio inbox during the period between 24 hours and 7 days after the customer's last inbound message.

We are not using HUMAN_AGENT for automated messages, promotional follow-ups, bulk messaging, or bot replies.

We understand that Human Agent does not allow indefinite follow-up and that messages beyond the 7-day window will still be rejected.

Once the feature is approved, we will validate it using a fresh Messenger conversation whose latest inbound message is older than 24 hours but less than 7 days old.

Please let us know whether the Human Agent review has already been submitted for the Meta App behind these accounts, and if possible, the current approval status or expected next steps.

Thank you！