Content type was not provided or is not supported

Hi,

The response:

Metadata
x-request-id : 38b78052-6ce9-4271-928d-b4e130ad9595
content-type : application/json
status : 415

Body
{
     "code": "CONTENT FILTERED",
     "message": "Content type was not provided or is not supported"
}

I have used the same pdf as an example as part of  the "Try it Out" forms on https://secure.na1.echosign.com/public/docs/restapi/v6#!/baseUris/getBaseUris and it works successfully.

My pdf is filled using Adobe software coldfusion on my end, and then loaded as a transient document successsfully, and then sent for signing.

My question is, how do I know what the issue is with my pdf when it works for the "try it out" functionality, but not when I use the API?

Can I see the document within my AdobeSign account anywhere for example? ( they do not appear under the Your Agreements section, under In Progress, because it hasn't been sent I assume ).

Happy to supply transientDocumentId etc if required.

Thanks,