[SOLVED]Android in Visual Studio 2017 does not work

Hello everyone. I am new with MonoGame and with the development for Android in Visual Studio and I am not able to run the default template of MonoGame for Android. Neither in the emulator nor in my phone.
I have installed Visual Studio 2017 several times, the necessary modules and MonoGame.
I have tried to change the Android version target, download more SDK, and much more. But I always get this error message:

Compilation error: Xamarin.Android does not support the execution of the previous version. Make sure that the solution is compiled before running or debugging it

In fact, the compilation is done correctly, the virtual device works but I can not see my desired blue background.
I think it should be something basic in the development for Android in Visual Studio 2017 that some more experience would take for granted, because I have not found a solution after several days searching on Google.
Sorry for my English and thank you very much.

(It seems to work now. I don’t know why. Thank you)