I've updated to the latest version and now thw countertop button comes up but there it stops. When pressed nothing comes up on the sidebar for marking the corners.
Countertops are working just fine for me. Can you provide some more detailed info on the steps you are doing? Can you post the file you are working with?
Once click the "construct countertop" button, you must then plot out the countertop. Hover your pointer over the corners of the cabinet and a circle will appear. Left click and then move to the next corner. Do this until you have outline the entire cabinet and then it will give you an option as to the texture.