Custom Action - Error 1001: Could not find file myApp.InstallState

I have tried to create a custom action for a Visual Studio Installer project to modify the permissions for a config file.

The Installer.cs is as follows:

public override void Commit(IDictionary savedState)
{
    base.Commit(savedState);

    // Get path of our installation (e.g. TARGETDIR)
    //string configPath = System.IO.Path.GetDirectoryName(Context.Parameters["AssemblyPath"]) + @"\config.xml";
    string configPath = @"C:\Program Files\Blueberry\Serial Number Reservation\config.xml";

    // Get a FileSecurity object that represents the current security settings.
    FileSecurity fSecurity = File.GetAccessControl(configPath);

    //Get SID for 'Everyone' - WellKnownSidType works in non-english systems
    SecurityIdentifier everyone = new SecurityIdentifier(WellKnownSidType.WorldSid, null);

    // Add the FileSystemAccessRule to the security settings.
    fSecurity.AddAccessRule(new FileSystemAccessRule(everyone, FileSystemRights.Modify | FileSystemRights.Synchronize, InheritanceFlags.ContainerInherit | InheritanceFlags.ObjectInherit, PropagationFlags.None, AccessControlType.Allow));

    // Set the new access settings.
    File.SetAccessControl(configPath, fSecurity);

}

public override void Install(IDictionary stateSaver)
{
    base.Install(stateSaver);
}

public override void Rollback(IDictionary savedState)
{
    base.Rollback(savedState);
}

public override void Uninstall(IDictionary savedState)
{
    base.Uninstall(savedState);
}

Then I add the Primary Output (Installer class = true) into the Commit section of the setup project's Custom Actions.

When I run the installer, I get the following error:

Error 1001: Could not find file 'c:\mypath\myapp.InstallState'

Scouring the web I've found a few examples of similar experiences, but none of the solutions offered have worked for me.

Any ideas?