Why is the device not visible?

Question

System administration

Hello, a device is connected to the router (via a patch cord) and it is displayed in the list of connected devices in the router’s admin panel, but the PC does not want to see it point-blank (arp -a tried, does not see it, ping does not work), there is no antivirus program, there is a rule in the firewall created, still use 0, please tell me what could be the trouble ???
(There is no way to reinstall Windows, connecting to another PC and checking it on it is also not an option)

Answer 1

What kind of device is that?