Cannot upload json file

I tried to upload a json file using the shortcut in a page [wordpress_file_upload] but it was not successfully. It notified the file cannot be uploaded. Other file type is ok.

So can you please help me to solve this problem. I am a developer myself, I tried to use below code:
function my_mime_types($mimes) {
$mimes[‘json’] = ‘text/plain’;
return $mimes;
}
add_filter(‘upload_mimes’, ‘my_mime_types’);

then I tried to upload json file in media successfully but still not ok for the upload using shortcut [wordpress_file_upload]

Can you please help to fix this problem?
Thanks a lot.