In burn menu the multiplexer settings section the write program end code options over on the right are greyed out. How do I correct this so I can select loop option?
No need to fiddle with the advanced encoder settings for that. There's an actual feature in the DVD-authoring part of the program to achieve looped playback of a movie on your disc. Just bring up the menu entry properties e.g. by double-clicking on the entry for the movie in the DVD burning preview screen. In that dialog, you can set an action for the end of the movie, including an option for the movie to be looped.