DIAGNOSIS Many smart plugs, lights, and older devices can only see a 2.4GHz WiFi signal. By default, Deco uses a 'Smart Connect' feature that combines 2.4GHz and 5GHz under one name, which can confuse these simpler devices during setup.
FIX You need to temporarily split the bands. 1) Open the Deco app and go to the 'WiFi Networks' tab. 2) Tap on 'Smart Connect' and turn it OFF. This will immediately reveal two separate networks: 'YourNetworkName_2.4G' and 'YourNetworkName_5G'. 3) Have your smart device search for networks and connect it to the '_2.4G' one using its usual app setup process. 4) Once the device is successfully connected and updated, you can go back and turn Smart Connect ON again. Your smart device will stay on the 2.4GHz band, and your phones/laptops will enjoy the combined network.
IF THAT DIDN'T WORK Some devices are extra finicky. If they still won't connect even to the separated 2.4G network, try moving the Deco unit and the device closer together during setup, and temporarily disable the 5GHz band entirely in the Deco app's Advanced Wireless settings just for the few minutes of setup.
HEADS UP Remember to turn Smart Connect back on after. Running with split bands permanently means your phones won't automatically roam to the best band, which is one of the main benefits of a mesh system like the Deco.