You do not need a group by parameter. The number of points in a polygon should be added as an attribute (default _overlaps) to the area output features.

If the count in the transformer is not working properly, the cause is quite often that the sources (points and polygons) are in different coordinate systems. Can you verify that both sources are in the same coordinate system? If not, use the Reprojector transformer to get them in the same coordinate system, before feeding the to the PontonAreaOverlayer.

Hi erik_jan

That did the trick - I added the Reprojector transformers and now I'm getting a count. Thanks for your help!