Your API documentation only shows this as a form submission but we are trying to do this without user interaction.

I think what I may be missing is the content type for the CreateUserProfileImageRequest attachment.

using C# this is what I tried. Error was "the format of value 'image' is invalid.

byte[] b = System.IO.File.ReadAllBytes(@"C:UserscacareyDocumentsiface.jpg");





            CreateUserProfileImageRequest cp = new CreateUserProfileImageRequest();

            RingCentral.Attachment att = new Attachment();

            att.filename = "iface.jpg";

            att.content = b;

            att.contentType = "image";

            cp.image = att;





            

            var rr = await restClient.Restapi().Account(accountID).Extension(extID).ProfileImage().Post(cp);