I am trying to add a Search Box to my site that searches the content added to each page.

This is the code that I have

@using Umbraco.Cms.Web.Common.PublishedModels;
@inherits Umbraco.Cms.Web.Common.Views.UmbracoViewPage<ContentModels.SearchPage>
@using ContentModels = Umbraco.Cms.Web.Common.PublishedModels;

@using Umbraco.Cms.Core.Models.PublishedContent;
@using Umbraco.Cms.Core.Services;
@using Umbraco.Cms.Core.Web;
@using Examine;
@using System.Collections.Generic;
@using System.Linq;

@inject IExamineManager ExamineManager

@{
    Layout = "Master.cshtml";
    string query = Context.Request.Query["q"];
    var searchResults = new List<IPublishedContent>();

    if (!string.IsNullOrEmpty(query))
    {
        if (ExamineManager.TryGetSearcher("ExternalIndex", out var searcher))
        {
            var criteria = searcher.CreateQuery("content").NodeTypeAlias("contentPage")
                                   .And().GroupedOr(new[] { "nodeName", "mainContent" }, query);

            searchResults = criteria.Execute().Select(x => Umbraco.Content(x.Id)).ToList();
        }
    }
}

<div class="container-fluid">
    <div class="row">
        <div class="col">

            <p>Search Results for <strong>@query</strong></p>

            @if (searchResults.Any())
            {
                <ul>
                    @foreach (var result in searchResults)
                    {
                        <li>
                            <a href="@result.Url()">@result.Name</a>
                        </li>
                    }
                </ul>
            }
            else
            {
                <p>No results found</p>
            }
        </div>

    </div>
</div>

but it is not returning any results, Can anyone tell me what I am missing?

1. I did check on the backend and ExternalIndex has all the values that I am looking for

2. contentPage is the Content Type that I want to search but I would also be OK searching all content types if possible