Problem with robots.txt in webmaster tools

Hi guys,
I am facing some issues with indexing of my site. In Google webmaster, robots.txt fetch is showing a yellow sign instead of green dot. I have researched on this and created a new robot.txt through yoast SEO plugin. Still there is a yellow sign in front of robots.txt fetch. Please check whether I have created robots.txt correctly. Robot.txt address: http://topadnetworks.com/robots.txt
How can I solve this issue. Please help!!!