Diagnosis
The mesh point is stuck in its pairing mode and can't find the main router's signal. This usually happens if they're too far apart during setup or if there's wireless interference.
How to Fix It
You need to start the pairing process over, but close up. 1) Unplug the mesh point. 2) Bring it within 3-5 feet of your main Alien router, in the same room. 3) Plug the mesh point back in. 4) On the main router's touchscreen, swipe down, tap on the mesh icon (it looks like a little satellite), and follow the prompts to 'Add Mesh Point'. The close proximity almost always gets them talking.
If That Didn't Work
Try a factory reset on the mesh point. With it powered on, find the tiny reset pinhole on the bottom. Use a paperclip to hold the button down for about 10 seconds until the light ring turns off and then comes back on solid white. Then try the pairing steps again from up close.
Heads Up
Once it's paired and working, then you unplug it and move it to its final location. Don't try to pair it from across the house.