Yes @Stephen, I am able to upload the file smoothly using my discourse but, it’s not allowing me to download. 
Please have a look at this screenshot, It’s having a download button. When I tried click on it, I am not able to download.
That’s the error raised when I tried to download the image using download button. ( Download button probably using send_data ruby function )
I just want to undrestand that this is something wrong with NGINX or any other directories permission related issue.
Thanks