This thread has a lot on the fill - mainly with the tree fill, but it might give you some clues to try. The engineer who developed these scripts was answering questions about it.
Thanks for your reply, but that's not the problem I have. My problem is that I get an error message:
"Error: Error in Symmetry initialization
Script: line 43: Variable name expected "
and not that the feature is not available, so it does not solve the problem, but thanks
Here's a link that mentions your issue. Looks like Adobe is working on fixing this, but you can contact the engineer regarding this for a workaround. See Radomir's comment at the bottom of the page:
Ok thanks, I'll check it