I don’t actually know how to answer that without send you to the FAQ. But if I sent you to the FAQ, you will say that you already checked it.
Anyway let’s try.
The answer is in the FAQ – #1.4:
Also check FAQ – #1.5:
Please make sure and confirm that you checked and did everything mentioned in the FAQ. In addition to that the image in your example is 1.5mb image with 8s response from your server. Check if it will work with something smaller.