Check your user manual to see what configurations the ram can be used in. Unless they are not allowed there, which I expect they should be, your board may have faulty slots. Unfortunately not all hardware arrives in working condition and its a pain when you have to stop your new build to sort that out. The manual should also help sort out what the lights mean. It may be tempting to just be happy running the two working slots but you might kick yourself down the track when it becomes an issue at upgrade time.