I´ve just installed Unity in my PC and create a project . I added just a box and clicked play. Now it says that I have to fix all compiler errors before playing. But there is nothing to fix. And the error does not say where is the error.
Try to lower scripting runtime version (in Player settings) to “.NET 3.5…” or if you have Win 7 try to install this update: https://support.microsoft.com/en-us/help/2533623/microsoft-security-advisory-insecure-library-loading-could-allow-remot