WorldInfo_0 Maps need lighting rebuilt

Hello all

i Have been using UE 4.15 for sometime .
and following some tutorials from the documentation and Created a landscape and then it showed that there objects need rebuilt so i press the “Build” Button but the same thing was showing so i tried to press “build lighting only” but same Message is still there .
so i took a look at output logs and find it Say WoroldInfo_0 Maps need lighting rebuilt
searched for solutions on google but none of them worked .

Sorry for my english

anyone can help ?