Seems like the interface has been changed - https://apidocs.mendix.com/6/runtime/com/mendix/core/component/ICore.html#initializeSession-com.mendix.systemwideinterfaces.core.IUser-java.lang.String-
Now you dont need the context or localle to initialize the session. So you can safely remove them from your code. Open your java file C:\Scratch\Mendix\myClarks-V5 to V7\javasource\usersignupresetpassword\actions\LoginUser.java into an editor and replace
ISession session = Core.initializeSession(context, user, null, ""); //with ISession session = Core.initializeSession(user, "");
That should be it.
If this action is comming from an appstore module perhaps you need to update that module?
Hope this helps,
Thank you, that cleared the error.