I'm cross posting this from New Members forum just to document the issue and fix;

For those interested here's an update on the no air from ceiling A/C vents in our 2016 29RS. I received no documentation on the Dometic air conditioner in my documentation packet so I went up on the roof and looked at the A/C unit and then went to the Dometic web site and searched their info until I found the unit that looked like mine. Then I down loaded the installation instructions from the Dometic site. It clearly showed a duct coming out either side of the unit within the roof structure. I removed the plastic grill inside the trailer and looked up into the plenum that houses the squirrel cage fan. Where the two ducts should be I found aluminum tape but could feel the ducts on the other side of the tape. I cut an X in the tape diagonally from corner to corner and folded it back into the ducts. I suspect this was the original idea but maybe the lunch whistle blew before the tape got cut at the factory. After reassembling the cover I now have forceful cold air coming out of all the ceiling vents. A minor oversite on someone's part but fortunately an easy fix. Now all is ducky.