Plugin not work in 3.5…

VFB is compatible with WordPress 3.5. Sounds like a plugin/theme conflict.

Also, you didn’t actually include a link.

Check this link

https://relief.pk/contact-form/

If shortcodes are not rendering, then it’s a theme problem.

How it’s Correct …???

First thing to check is that you are calling the_content() within The Loop.

You are probably better served asking this in the general help forum instead of this plugin section.