I found the solution to my problem: What prevented the WebMethod was called was the reference to "System.Web.Optimization". Not sure how he does it, but as I will not use it at the time, decided to remove:
"System.Web.Optimization" and "Microsoft.AspNet.Web.Optimization.WebForms"
It is also necessary to remove the web.config as follows:
<namespaces>
<add namespace="System.Web.Optimization" />
</namespaces>
<add assembly="Microsoft.AspNet.Web.Optimization.WebForms"
namespace="Microsoft.AspNet.Web.Optimization.WebForms" tagPrefix="webopt" />
<dependentAssembly>
<assemblyIdentity name="WebGrease" culture="neutral"
publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="0.0.0.0-1.5.2.14234" newVersion="1.5.2.14234" />
</dependentAssembly>
All ok now! Thanks to everyone who helped me with the problem! :)