Removing the check mark from include audio enables my time lapse to be clicked and it works, I just tried it.
Another way to make time lapse videos is under the record tab select "periodic each", and min to 1 to 60 seconds and seconds to zero so it records one frame every however many seconds you select in min. I use 5-15. Works well if you don't need continuous recording on that camera during the time lapse shooting. Otherwise your left with the time lapse export option from your continuous video or clip.