If you look at the next post you sort of have the same encoding problem as I do. If you can roll back to version 12.0.6.1 and give it a try you may be successful. Something has changed in 12.0.6.3 and the DVDfab people are looking at it.
fussybob
Thank you! I did try a different mkv file and it works. But if I continued having problem, I will roll back. ;)