@Russ May be worth updating the instructions to indicate that "on" and "off" are case sensitive if you want it to automatically choose between the On and Off commands. (Alternatively ignore case for on and off to choose between on command and off command)
e.g. I used IFTTT and sent "ON" or "OFF" as parameters, and it just sent those as arguments to my ON command.
Once I fixed it to "on" and "off" it properly instead chose between the commands instead of using them as arguments.