Looks like you have a 23RB. Mine is also a 2015.
As suggested, remove the vent cover and confirm that the duct is connected.
The issue I had was a pinched duct hose and excess duct hose. I had to drop a portion of the comoplast to reroute it.
But the real fix was adding adjustable dampers at the furnace to balance the air flow. Also took the opportunity to add a heat register to the bathroom.
Photos of what I did are in my photo album if interested.
http://www.keystoneforums.com/forums...hp?albumid=695