Messenger error 100: Unsupported get request - object missing or unreadable

Code 100 with subcode 33 is the Graph API's three-way ambiguity: "Object with ID * does not exist, cannot be loaded due to missing permissions, or does not support this operation." Meta deliberately refuses to distinguish the cases, confirming that an object exists while denying access would leak information, so the error reads identically whether your ID is wrong, your token is underpowered, or the endpoint does not do what you asked.

On Messenger integrations it typically appears on reads: fetching a conversation, message or Page object by ID. The permissions reading is the most common in practice, the object is real, but the Page token in hand belongs to a different Page, lacks a required scope, or the app's access level (Standard vs Advanced) does not cover the object class. The does-not-exist reading follows data bugs: IDs from another environment, deleted conversations, or numeric mangling of long IDs. The unsupported-operation reading catches category errors like GET on write-only endpoints.

Diagnosis is by elimination, and the Access Token Debugger plus the Graph API Explorer are the tools: run the same query with a known-good token of the right type; if it works there, the problem is your production token's identity or scopes, not the object. Note the difference from 100/2018001, which is specifically about message recipients; subcode 33 is the general object-access version.

{
  "error": {
    "message": "Unsupported get request. Object with ID '1234567890' does not exist, cannot be loaded due to missing permissions, or does not support this operation.",
    "type": "GraphMethodException",
    "code": 100,
    "error_subcode": 33,
    "fbtrace_id": "BLBz/WZt8dN"
  }
}

Keep object IDs scoped the way tokens are: tag stored IDs with the Page and environment that produced them, and never let production code read staging IDs. Add access-level assertions to integration tests so a Standard-Access regression fails CI, not customer flows. The ID-scoping rules that make Messenger data non-portable are summarized in the limits reference and on the 2018001 page.