As rolleistef said, it is corrosion at the contacts that generally causes selenium meters to die. When I was repairing cameras, I fixed a lot of meters by using the pencil eraser method. LIGHTLY cleaning the contacts and the contact area on the cell with a soft pencil eraser, and you'll probably be back in business.
I have a Yashica Minister III, and several Weston meters from the 50's that all work great. I have cleaned a couple of the Westons.