DIAGNOSIS The satellite has failed to establish a connection with the main Deco. This is usually a setup or placement issue, not hardware failure.
FIX Unplug the satellite. Move it within 3 feet of the main Deco unit. Plug it back in. Wait for the light to pulse blue. Open the Deco app. Go to the Devices tab. Tap the red Deco node and follow the on-screen prompts to add it again. Keep it close during the re-pairing process.
IF THAT DIDN'T WORK The satellite may need a factory reset. Hold the reset button on the back for 10 seconds until the LED flashes amber. Release. Add it as a new device in the app. Use a fresh Ethernet cable if connecting via backhaul.
HEADS UP Solid red after a successful setup usually means it lost connection. Check for physical obstructions or new interference sources, like a microwave or metal furniture, between units. Distance is the #1 culprit.