No output schema found

I keep encountering an error when sending an experience event from the Native App SDK.

I have setup a Datastream, dataset and schema and am using the Edge.sendEvent method from within my natve app, with an xdm object and a data object.

In the response to the edge network request, I continually receive the message:

"type": "https://ns.adobe.com/aep/errors/XFRM-100003-404",
"status": 404,
"title": "No output schema found",
"detail": "The output schema with ID https://ns.adobe.com/<company name>/schemas/155557c6abb8f03349c15d6547f35889ec51e204fb71a778 was not found."

I can definitely see that the schema with that id does in fact exist - so am really unsure why I keep receiving this error.

The result of all this is that my additional data object is not flowing through to Adobe Analytics.

Can anyone please shed some more light on this error please?