@Nickyvdh 

Thank you for reaching out. I understand that after switching your home internet from DSL (phonelines) to fiber (fiberglass), your main Deco Mesh unit sometimes fails to connect to your cable modem (Experia Box V10), showing a red LED and no internet connection. Restarting the Deco via the app temporarily restores the connection.

Here are some steps you can follow to help resolve this issue:

1. Check your ISP connection: Connect a computer directly to your Experia Box V10 modem/router using the same Ethernet cable. Make sure you have a stable internet connection from your provider.

2. Reboot your modem and main Deco: Power cycle both your ISP modem (Experia Box V10) and your main Deco Mesh unit. Wait a few minutes for both devices to fully restart.

3. Try a different Ethernet cable and port: Replace the Ethernet cable between your modem and the main Deco, and try using a different Ethernet port on the main Deco if available.

4. Update DNS settings: On your phone (connected to the Deco Wi-Fi), open the Deco app and go to MORE > Internet Connection > tap 'IPv4 Connection' > DNS Address. Select 'Manual' and enter '8.8.8.8' and '1.1.1.1' as the primary and secondary DNS servers.

5. Mac Clone (if needed): If your PC has internet when connected directly to the modem, but the main Deco does not, try using the Mac Clone feature. Please refer to this article for instructions: https://www.tp-link.com/en/support/faq/2925/

6. Additional settings to check:
• In the Deco app, go to MORE > Advanced > IPTV/VLAN. If the IPTV port is enabled, do not use it to connect to your ISP modem.
• Go to MORE > Advanced > WAN Port. If this feature is enabled, ensure you are using the correct Ethernet port on the Deco for the modem connection.

If you continue to experience issues after these steps, please contact TP-Link Support and provide the results of the troubleshooting above. This will help us assist you more efficiently.