Can't Manage Videos On iPad Within iTunes

Hey everyone!

So I have an iPad 3 (June 2013) and its been working great! But now all of a sudden starting yesterday ish, when I connect to iTunes and it recognizes it; it pops up and everything, I cannot add videos to the device whatsoever. And these were videos that work on the device and were loaded previously no problem. They are movies and tv shows from an external hard drive, all files were converted to mp4 (ipad 3 specific) using Freemake Video Converter. I am stumped

Anyone know what causes this to happen? Any solutions?

Thanks