I tried using the same approach as the this create fax message endpoint but with no luck. I just get 'Error 415 Unsupported Media Type' and I'm trying to upload a PDF file which should be a standard accepted file type as I can upload it directly in Glip. BTW, at the moment I'm doing this in the sandbox, not sure if that is important.
Please any help to point me in the right direction would be much appreciated. If there is any more information that you guys need and think that may help please ask.
Thanks in advance.
Create Post API Endpoint: