DIAGNOSIS The LiDAR sensor on top isn't getting a reading, usually because it's physically obstructed or its spinning mechanism is jammed.
FIX First, check for obvious blockages. 1) Power the robot off. 2) Look at the clear plastic dome on top—the LiDAR tower. Wipe it clean with a dry microfiber cloth. 3) Now, gently try to rotate the silver disc underneath the dome with your finger. It should spin freely and smoothly. If it's stuck, carefully clear any hair or string wrapped around its base. 4> Power it back on. You should see the LiDAR spin up immediately and hear a faint whirring sound.
IF THAT DIDN'T WORK The robot might be starting in a very dark room. The LiDAR uses lasers, but it still needs some ambient light for its other sensors to initialize. Try moving the dock to a brighter area or turning on some lights for the first few mapping runs.
HEADS UP Never place objects on top of the robot or store it under a shelf that rests on the LiDAR dome. Even slight pressure can misalign the delicate mechanism inside, leading to permanent mapping failure.