The blueprint work of the trigger sensor. So if the trigger sensor is OFF then the light will not come ON. The sun is a condition and not a trigger, so it will not come ON when the sun sets and your motion sensor is OFF. There are ways to use the sun as a condition trigger but your motion sensor (Trigger Sensor) must be ON.
If you would like a sun trigger then you can use this blueprint. 
Turn Light, Switch or Scene On & Off with Trigger Conditions
If I am not on track with you then just let us know if you need more help.
Blacky 