Any reason this annoying light would come on besides a bad bulb

ive circled my truck several times with the lights on, blinkers on, brakes on, reverse lights on, and all of them combinded everything is fine but a few days ago i notice my one of my license plate lights was out. i replaced that bulband the lamp out light is still onthere are no noticeable lights out and ive already disconnected the negative termanil for a few minutes hoping that maybe it would reset but no luck

anyone with an opinion or help please post it

 

I just had the same problem with my 04 1500 QC Hemi. I found a lot of corrosion on the left tail light bulb bar inside the light assembly. I took the light assembly out and removed the plug and found excessive rust and corrosion on the pins and the female part of the plug. I cleaned them off and everything works fine but I ordered new new bars for lights so it does not happen again.