I am attempting to block a device that I cannot identify but the 'Blacklist' option does not seem to work. I added the device to the 'Blacklist', clicked 'Save' and rebooted the router but the device

Hi, I have just got an Archer VR900 and I am going through blocking unknown MAC addresses. I can see how to block them but I can't find a way of disconnecting them without rebooting the router. I get