Have you tried doing this operation with the API Directly?
This should make the same API call as the SDK,
Can you verify the file you are uploading conforms to,
The file must be in PNG, JPG, SVG, or GIF format, and less than 1 MB in size. For best results, use an image with a transparent background and a square dimension of 200px by 200px to prevent upscaling.
If so and no error is returned, even when using the API directly do you see any messages in the Orgs System log.
If all of the above seems to succeed and there are no errors in the logs let us know.