Project not selected to build for this solution configuration

Question

As Kowalski said, You must check Deploy Option on Configuration Manager. RightClick on the solution and select Configuration Manager. Then Check Deploy Option for the startup Project. As this image

go To Build => Configuration Manager . then check the deploy checkbox for the startup project . Ps. make sure to select your startup project by right clicking on the project => set as startup project

Select Deploy also from Configuration Manager for android project