So, I've been developing this small booking plugin lately, it's ready for deployment and decided to switch from debug=true to false. Boom it went, and my menu tree disappeared. Even now, if I switch back to web.config -> debug=false it's still gone

The exception thrown states:

Received an error from the server. An error occured. Could not render a tree for type bookings

This is my menu tree code - as you see, pretty standard code snippet:

[PluginController("Bookings")]
[Tree("bookings", "bookings", "Bookings")]
public class BookingMenuTreeController : TreeController
{
    protected override TreeNodeCollection GetTreeNodes(string id, FormDataCollection queryStrings)
    {
        //check if we're rendering the root node's children
        if (id == Constants.System.Root.ToInvariantString())
        {
            var tree = new TreeNodeCollection
            {
                CreateTreeNode("1", id, null, "Bookinger"), 
            };
            return tree;
        }
        //this tree doesn't suport rendering more than 1 level
        throw new NotSupportedException();
    }

    protected override MenuItemCollection GetMenuForNode(string id, FormDataCollection queryStrings)
    {
        var menu = new MenuItemCollection();
       // menu.AddMenuItem(new MenuItem("create", "Create"));
        return menu;
    }
}   

I initialize the menu tree on application startup like this:

public class Startup : ApplicationEventHandler {

   protected const string BookingSectionAlias = "bookings";

    protected override void ApplicationStarted(UmbracoApplicationBase umbraco, ApplicationContext context) {
        Section section = context.Services.SectionService.GetByAlias(BookingSectionAlias);
        if (section != null) return;

        context.Services.SectionService.MakeNew("Bookings", BookingSectionAlias, "icon-newspaper");

    }

Custom tree is present in tree.config. I'm uncertain where to look next. Any ideas? [Umbraco 7.5.12]

Thanks, Simon