DIAGNOSIS That solid magenta light means the satellite can't sync with the main router. It's almost always a sync issue during the initial setup, not a hardware failure.
FIX You need to force a fresh sync. First, unplug both the router and the satellite. Plug the router back in and wait for it to boot up fully—you'll see a solid white light. Now, take the satellite and press the small Sync button on the back. Within a minute, plug the satellite back into power while holding that Sync button down. Keep holding it for about 5 seconds after you plug it in, then let go. The light should pulse white, then turn solid blue when it connects.
IF THAT DIDN'T WORK If the light stays magenta, the satellite might be too far away for the initial sync. Move it right next to the router, within a few feet, and repeat the sync process. Once it connects and shows blue, you can move it to its final spot.
HEADS UP The initial sync only uses the 5GHz backhaul band. If you're trying to sync through multiple thick walls or a floor, it often fails. Always do the first sync in the same room.