The type , provided as the Service attribute value in the ServiceHost directive could not be found.

A reminder to self:

When deplyoing a WCF service, and the assembly is registered in the GAC, don’t forget that in the .svc file one needs to put the full assembly path   in the Service element:

<%@ServiceHostLanguage=”C#”Debug=”true”Service=”TYPENAME, ASSEMBLY NAME, Version=1.0.0.0, Culture=neutral, PublicKeyToken=12345678901234″CodeBehind=”HelloWorld.svc.cs” %>