Issue fixed after checking with web hosting setting.
“Found the problem, basically the wordpress plugin triggered the mod security.
Access denied with code 406 (phase 2). Pattern match “^Shockwave Flash” at REQUEST_HEADERS:User-Agent. [file “/usr/local/apache/conf/modsec2.user.conf”] [line “203”]
I have bypass the shockwave security.”
So you may check with your hosting provider to change that setting.
Hope it work for you!