@TK33 I had the same issue. Changing the DNS didn't work for me. I got mine working by enabling IPTV/VLAN setting in Deco app.

Update - 20 Nov 2020 After exhausting all possible support channels (TP-Link Customer Service/Technical Support/TM Support) and with no workable solutions - I finally fixed it by enabling IPTV/VLAN...

@TP-Link_Deco Just tested again using the other Deco as main - same issue. It was solid Blue during the initial setup but turned solid red when it is at the step of 'Creating your Wi-Fi network'....

@TP-Link_Deco Hi. I got valid IP when connected to the modem directly, and able to access the Internet. Main Deco got a valid IP as well. I have not tried to connect the other Deco as main. Will try...

@TP-Link_Deco Thanks for the reply. Done that, but still the same. As soon as it reached the step to try connecting to the internet, the LED turned solid red.

The Decos were working perfectly fine until recently when my devices keep disconnecting from the nearby Deco. It has gone to worse this morning when both the Decos are in solid red LED. I have tried...