This took me awhile to find and fix, luckily I ran across the google groups posts which has since been closed and someone had found the issue for me already as I looked here and could not find a solution. I figured I would post this to help any future users out with the same issue.
On a GT62VR MSI Laptop I could not get Voice Attack to hear me when all other application could hear me just fine. The problem turned out to be the
Nahimic 2 software that comes preloaded. It appears to interfere with VA somehow. Would love to know why and for it to VA to be able to work with it btw.
In any case,
I just exited the software via the control panel icon and VA started hearing me and working fine.
Very frustrating thing to track down. Hope this helps someone in the future.
Also in case you need extra help, I found the Google Groups to be a great resource of information. It is at:
https://groups.google.com/forum/#!forum/voiceattack