Simulated objects will only collide if they are part of the same simulation. Set up a simulation, set the cloth plane as softbody (third tab), then set up the ball as part of the simulation in either the first or second tabs.

Bullet uses convex hulls of simulated objects, for speed while calculating collisions. If the objects fail to interact, the problem might relate to the convex hulls. You can create and study samples of the convex hulls, using the... Object menu? Up on the file menu bar, one of the headings will list "Create convex hull" on its pull-down menu. Clicking that option will create an un-transformed (no translations, rotations, or scaling) copy of the convex hull for the currently selected actor, showing Poser's internal representation of an object for Bullet's purposes. Unfortunately, I'm not sure what remedy to suggest if your simulation problems result from failed convex hull collisions....

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Cage can be an opinionated jerk who posts without thinking.  He apologizes for this.  He's honestly not trying to be a turkeyhead.

Cage had some freebies, compatible with Poser 11 and below.  His Python scripts were saved at archive.org, along with the rest of the Morphography site, where they were hosted.