Custom Created Sections are locked on page builder

I have created a new custom section called "SingleColumnSection" When I go on the Kentico UI's page builder to add it, it gets added but the blue plus sign in the middle is locked. Meaning, I can't click on the plus sign to add a widget.

Here is the code for the section:

View

@using Kentico.PageBuilder.Web.Mvc
@using Kentico.Web.Mvc

    <section class="section section--padded">
        <div class="section-inner">
            @Html.Kentico().WidgetZone()
        </div>
    </section> 

Here is the controller:

using AE.Web.Gwic.Controllers.Sections;
using Kentico.PageBuilder.Web.Mvc;
using System.Web.Mvc;

[assembly: RegisterSection("GWIC.SingleColumnSection", typeof(SingleColumnSectionController), "Single Column", Description = "1 Column with Padding", IconClass = " icon-square")]

namespace AE.Web.Gwic.Controllers.Sections
{
    public class SingleColumnSectionController : SectionController
    {
        // GET: Single
        public ActionResult Index()
        {
            return PartialView("Sections/_SingleColumnSection");
        }
    }
}

How can I unlock the section to be able to add widgets in it?