Hello @Diaseb ,

Welcome to our community.

Here are some steps to help you troubleshoot:

1. Check Ethernet Port and Cable
• Make sure the Ethernet cable is securely connected to both the Mac mini and the router.
• Try using a different Ethernet cable to rule out a faulty cable.
• Test another LAN port on the router, if available.
• If possible, connect a different wired device (such as a laptop or PC) to the same port and cable to see if it is detected by the router.

2. Check Router Ethernet Lights
• Look at the Ethernet (LAN) LED indicators on your router. If the light for the port where your Mac mini is connected is off, it could indicate a problem with the port, cable, or the Mac mini’s Ethernet port.

3. Reboot Devices
• Restart both your Mac mini and the router. 

4. Check IP Configuration on Mac mini
• Go to System Settings > Network > Ethernet > Details (or Advanced), and ensure 'Configure IPv4' is set to 'Using DHCP'.
• If you are setting a manual IP, make sure the IP address, subnet mask, and gateway are in the same range as your router.

5. Test with Another Device
• If another device works with the same cable and port, it may be with the Mac mini’s Ethernet port or settings. In this case, you may need to contact Apple support for further assistance.