The App store version of Smart Converter Pro has VOB conversions disabled. This was to meet the App store rules.
The version on the Shedworx website still converts VOB files.
If you're using the free version just download the free Shedworx version here (http://shedworx.com/download?product=sc).
If you've already bought the Pro version all you need to do is send through some proof of purchase.
To get the VOB enabled version of Smart Converter Pro just email us a screenshot of your App store receipt or your purchased history (showing Smart Converter Pro 2) and we'll send you a key for the Shedworx version.
How to view your purchase history: https://support.apple.com/en-au/HT204088
Screen shot how-to: http://support.apple.com/kb/PH11229
Contact us here with your screenshot.