If you installed the handler after you added the device to SmartThings, you’ll need to exclude it and then reinclude it back to SmartThings. We post detailed instructions on how to create and assign custom device handlers for battery-powered devices here so you can verify each step of the process: https://www.thesmartesthouse.com/blogs/the-smartest-blog/how-to-install-a-custom-device-handler-in-smartthings
This is how the device should show up in your app:
