Normally, a coin acceptor has a coil that directs the coins to the return slot or the money box. Further, you have the coin return button on front of the acceptor that opens the acceptor and allows coins that are blocked inside to return to the user. This last thing was especially needed with mechanical acceptors that didn't let pass coins of a bigger size unless you pressed that coin return button. During learning, it can be normal that the coins are returned to the user. When the learning process is finished, they should be accepted. Some acceptors will only accept after you assigned an output to the coin you just learned. Some have an inhibit input that needs to be connected to ground. If that line isn't connected, the acceptor won't accept any coins. The idea is to have an option to disable coin acceptance when the game board isn't ready or in error state.
