It looks like you are only getting the first light, but as you are looping through the array, you are toggling the light a number of times. (The same number as the length of the array). This means that if you have an even number in the array, you will toggle the light an even number of times. You are switching it on and switching it off again!
If you just want to control the first light only, delete the Make Array and the For Each Loop, and just connect the GET to the Target.