@Kmcs 

I understand that after a recent outage, your Deco Mesh system is not connecting to the internet, and the units are stuck on a solid yellow light. The Deco app shows that the units are communicating with each other, but not with your modem, and you have already tried resetting and using the app without success.

Here are some steps you can follow to restore your internet connection:

1. Check your ISP connection: Connect a computer directly to your ISP modem/router using an Ethernet cable. Make sure you can access the internet from the computer. If not, the issue may be with your ISP or modem.

2. Reboot your devices: Power off your ISP modem and the main Deco unit. Wait about 2 minutes, then power on the modem first. Once the modem is fully online, power on the main Deco and wait for it to boot up.

3. Check cables and ports: Try using a different Ethernet cable between the ISP modem and the main Deco. You can also try a different Ethernet port on the Deco if available.

4. Update DNS settings: Make sure your phone is connected to the Deco Wi-Fi. Open the Deco app, 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 can access the internet when connected to the modem, but the Deco cannot, try enabling MAC Clone on the Deco. For details, please refer to this article: 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, make sure you are using the correct Ethernet port on the Deco to connect to your ISP modem.

If you have tried all the above steps and still cannot restore your internet connection, please contact TP-Link Support and provide the results of these troubleshooting steps. We are here to help you further.