Both Belt Tensioner Lock Indicators must be FULLY green when installing the base with a vehicle seat belt.
If the indicators are red or partially red, this may indicate that the panel isn’t fully closed. Try pushing down firmly on the panel to see if the panel can be closed further. If the indicators continue to show red, open the Belt Tensioner, allow a small amount of slack in to the belt, and then close the Belt Tensioner again.
If the Lock Indicators still show red, or if there is more than 1” of movement when checking for movement where the belt passes through the Liing’s base, then try a different seating position or install the base using rigid LATCH (UAS).