Altium. Can't apply a rule of plane connect to Polygon
You need to use another section of the rules.

The picture below shows which one:


In the Altium Plane and Polygon differ slightly from each other.

Plane - Less flexible, but quickly processed by the program and does not take large computing power. Also on this layer you can not rout.

Polygon - More flexible for editing, but repour requires more computing power.