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:\Users\cacarey\Documents\iface.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);