Ok, let me rephrase that.
In .NET, don't you have a config file that let's you give names to things for your add-in, such as id, class, caption , category, image and etc? Your add-in should be in whatever you name you gave to your category.
You don't add add-ins from the Add-in Manager. If your add-in is listed in the Add-in Manager, then it should already be loaded. You add the add-in from the customize window as you have already shown.
Try deleting your add-in from the Add-in Manager, recomplie your add-in and redeploy it. Make sure you remember which category you used for deployment and then check in that category in the cutomize window.