I have tried multiple ways but I cant figure it out.

Code I use to save the image and convert to Byte[]:

        Byte[] bytes = new WebClient().DownloadData(attachment.Url);
        File.WriteAllBytes(attachment.Filename, bytes);
        Thread.Sleep(100);
        HttpResponse<string> response = Unirest.post(PostImageURL).header("X-Mashape-Key", "API_KEY").field("image", File.ReadAllBytes(""+attachment.Filename)).asString();

for some reason it always returns image already exists when it definitely doesnt.