Any reason why I can't activate the Artistic Filter in Photoshop 6.0?

I created a print with the spatter brush from a photograph that was scanned but now I'm unable to duplicate the procedure.
The "Artistic Brushes" remain "greyed out" unless I turn on the quick mask which then masks the layer and leaves me unable to add the filter.
I made a duplicate layer of the image and selected the image but
am still unable to get the filter to work.
Why is this happening?
I know it's something simple but I'm a novice with this program
am still trying to figure it out.

Thanks for your help,
Peter