The block feature uses the guests device MAC address to prevent them from logging into your WiFi. Upon connecting to your network, we do a check against their MAC address to see if it is blocked. If it is, we redirect them to the lock page, which is the same page guests see if they surpass any network limits you have set.
To block a guest, head to their guest profile and click on the Options icon next to the guest's name.
Select Block to block the guest.