Deco mesh node blinks red while joining network

The most likely cause is that the older W3600 unit is still set up for its previous network or is too far from the main node, so it cannot complete the handshake with your newer BE25 network. A solid red light usually means the unit is in a failed or setup-needed state rather than actively searching. 1. Factory reset the W3600 first. Hold the small reset button on the back or side for about 10 seconds until the light changes, then wait a few minutes for it to restart. 2. Place the W3600 within about 3 to 5 feet of your BE25 main node, with no walls between them, for the initial join. Move it to its final spot once it is connected. 3. Power cycle both the node and the main BE25 unit by unplugging each for 30 seconds, then plugging the main unit back in first and waiting until its light is solid before plugging in the W3600. 4. Open the Deco app on your phone (make sure Bluetooth and location are on) and use the Add a Device option instead of trying to pair from the physical button alone. 5. If the app asks for an update, install the latest Deco firmware on the BE25 and the W3600 before adding the node, since mismatched firmware can block joining. 6. Confirm that your phone is on the same Wi-Fi network as the Deco system during setup, and avoid using a VPN while adding the device. 7. If it still flashes red, try the W3600 on a different power outlet, since weak power can cause odd light behavior. If none of this works: I am not certain why the W3600 specifically is rejected by the BE25, so contact the manufacturer's support, give them the model numbers and the exact light pattern, and ask whether the W3600 is compatible with the BE25 generation.