Prosafe FS728TLP port mirroring does nothing

I selected a source port and destination port, tried session mode in both enable and disable, and tried TX, RX, and TX and RX, and then clicked apply. Nothing happens with any of these. I have tried updating the firmware and doing a factory reset. In the very least, I should lose connection on the pc that is plugged into the destination port as it is now a mirrored port, but instead, it continues to have the same IP and never loses connection.