Facebook Messenger API returns OAuthException with "An unexpected error has occurred" after permissions review

Question

I am currently developing a application that interacts with the Messenger API. Everything was working as expected until I submitted my app for a permissions review to Meta for the pages_messaging permission. After Meta’s review team tested the app by sending messages to the associated Facebook Page, the Messenger functionality for that Page stopped working entirely.

Here is what happens:

When I use the Access Token to make a request to me?, the response is successful, and I can retrieve basic Page information. However, when I try to query Messenger conversations using the /PAGE_ID/conversations endpoint, the following error is returned:

{
  "error": {
    "message": "An unexpected error has occurred. Please retry your request later.",
    "type": "OAuthException",
    "is_transient": true,
    "code": 2,
    "fbtrace_id": "AX_i_atlXLLuT2YAz5tkvl6"
  }
}

Additional Observations: The issue occurs only for the Page tested by Meta's review team. Other Pages linked to the same application work without issues. The Access Token is valid and includes the necessary permissions (pages_messaging and pages_read_engagement). According to Meta Status, there are no ongoing disruptions for the Messenger API. The error is marked as is_transient: true, but retrying multiple times over hours/days still produces the same error. I have reviewed the Page's settings and permissions, and everything seems configured correctly.

Questions: What could cause the Messenger API to stop working specifically for a Page after Meta's review process? Is there any action I need to take to resolve this issue, such as resetting permissions, reassigning roles, or contacting Meta support? Could this issue be related to the permissions granted during the review process? If so, how can I verify this? How should I approach debugging this error further? For instance, is there a way to trace the problem using the provided fbtrace_id?

Any insights or guidance would be greatly appreciated!

I used the Access Token to call the Messenger API multiple times for the /PAGE_ID/conversations endpoint. I also verified that the Access Token has the required permissions (pages_messaging and pages_read_engagement) using the Graph API Explorer. I tested the /me endpoint with the same token, and it returned the expected Page data, confirming the token is valid.

I expected to receive a list of conversations for the Page, as it works correctly for other Pages linked to the same app. The Access Token should function properly because it is newly generated and has all the required permissions.

Instead of the expected response, the API returned the following error: json

{
  "error": {
    "message": "An unexpected error has occurred. Please retry your request later.",
    "type": "OAuthException",
    "is_transient": true,
    "code": 2,
    "fbtrace_id": "AX_i_atlXLLuT2YAz5tkvl6"
  }
}

Additional Details:

This error happens only with the Page that was tested during the permissions review by Meta’s review team. Other Pages linked to the same application are working as expected and do not encounter this issue.