Black Tank Flush

There's supposed to be a rotary kind of spray head in the tank that I certainly can hear on ours. It's not a really loud noise, but it does make one and not just like water running into it. Short of sticking a camera probe down the toilet & trying to watch it, I don't know how you could verify it was actually spraying. Since your unit is brand new, I'd call the dealer & ask them about it. I wouldn't make a trip though unless I knew they'd look into it.