The boards are just made of wood or plastic, same as the planchette. They have no function on their own power. It is the human mind that determines the “power” of the board. If someone believes in the board’s power, then the board will be perceived to have power. Whether consciously or not, that person will move the planchette. If there are multiple people sharing the planchette, I feel someone will be moving it.
When I was young (12/13) years old, a friend of mine had a board and we played with it everyday after school and it always worked. Fast forward 45 years or so, I was assistant manager for KB Toy store and we had a shipment of Ouija boards. I bought one for my son and I. We sat there for quite awhile and nothing happened. I said to my son my friend from years ago had to have been moving the planchette because I know I never did. I returned the board and jokingly told my boss it was broken.
This is not proof whether they work or not but I am in the business of the occult where I deal with the unknown vs the known and the one thing I can say is the human mind is very powerful. If you believe in something strongly enough you might be able to manifest it in the material world. The Ouija boards have no power, they were a parlor trick but if someone believes a spirit is talking to you through it, that belief is manifested through you, not the board.