Sending Data via MQTT is not working

Setup, Configuration and Use Items & Sitemaps
2

Two possible options:

  1. Have you tried restarting openHAB?
  2. Are you sure you want your topic to be /backyard/findusGrab/lightMode? Topics often don’t usually start with /, so I would also try backyard/findusGrab/lightMode

What is the other device that you have used to send data which worked, and can you show us the Mosquitto log when it works, and when it doesn’t?