My parents had a new printer installed by a “professional” but it wouldn’t show on the network. I tried everything, reinstalling drivers, unplugging and plugging cables again…

After hours of nothing working, i got desperate and just flipped through the menu of the printer on this small LCD display. There is a DHCP setting. The DHCP is set to a fixed address. The router every now and then reboots and gives new dynamic addresses. The printer refused its dynamic address all this time.