Low Coolant Light - Very Odd - HELP PLEASE

I replaced the coolant elbow going into the tensioner pulley. Filled radiator until full. Opened bleed screw above thermostat. Filled radiator with coolant until coolant came out from bleed screw. Put bleed screw back in. Filled overflow reservoir. Started car and let run for about 15 minutes. Temperature guage in car went up to normal. Low Coolant light is still on. Could the thermostat be stuck? Thanks for the help.

What's the coolant level look like after it has cooled down? These engines are notoriously difficult to get burped properly. It takes some patience.

My low coolant light was on even with the radiator full. The sensor is about two inches down from the radiator cap. I decided to just unplug the wire and check it like I normally would if the sensor wasn't there.