Custom Search Index Module Not Working

Hi everyone,

I'm currently using Kentico 11 to try and implement a Search index with custom fields pulling in. For some reason my Custom Module code isn't running - I've followed the tutorials on here https://docs.xperience.io/k11/configuring-kentico/setting-up-search-on-your-website/customizing-the-content-of-search-indexes but unfortunately the code just isn't running. Below is my code, I can't see anything in the Event Logs to suggest that it's not working, I've tried both with and without the AssemblyDiscoverable attribute, with and without a namespace.

using CMS;
using CMS.DataEngine;
using CMS.DocumentEngine;
using CMS.Membership;
using Models.Models;

// Registers the custom module into the system
[assembly: RegisterModule(typeof(VNCustomSearchIndexModule))]
[assembly: AssemblyDiscoverable]
public class VNCustomSearchIndexModule : Module
{
    public VNCustomSearchIndexModule() : base(typeof(VNCustomSearchIndexModule).Name, false) { }

    protected override void OnInit()
    {
        base.OnInit();

        // Assigns a handler to the GetContent event for pages
        DocumentEvents.GetContent.Execute += OnGetPageContent;
    }

    private void OnGetPageContent(object sender, DocumentSearchEventArgs e)
    {
        TreeNode indexedPage = e.Node;

        Accommodation accommodation = e.Node as Accommodation;
        Attraction attraction = e.Node as Attraction;

        if (indexedPage != null)
        {
            UserInfo pageOwner = UserInfoProvider.GetUserInfo(indexedPage.NodeOwner);

            if (pageOwner != null)
            {
                e.Content += " " + pageOwner.UserDescription + " ";
            }
        }
    }
}

Any and all help would be greatly appreciated.

Thanks, Adam