iOS failed to compile

I am developing two Xamarin Forms app with Android and iOS using Visual Studio.
Yesterday my code was compiling fine, today I am not able to compile none of the two projects in iOS.

One thing I found rare is that if I want to debug I only have Device option to select:

and then if I try to compile I get the following message:
"There were build errors. Would you like to continue and run the last successful build?"

Any ideas what could happened?