AC Not Pushing Much Air

seal the ductwork right after the last vent in each duct run my duct extended at least 3' beyond the vent and was blowing into the ceiling wasting a lot of cold air it made a huge difference.

Filter dirty?

If the fan blower motor is working/blowing I would drop it (usually three screws) and see if anything is blocking the ducting. Don't know about a MH but the early to mid 2000s Dodge trucks had a habit of the recirculate "door" in the dash would break at the hinges and fall, blocking the airflow of the blower motor. 5 minute fix, remove the blower motor, reach up and pull the broken door out.

If you have the rapid cool vent next to the air return open, you will not get much air flow to the ducted vents by design. The rapid cool vent is only intended for initial localized cooling when needed, and should then be closed for normal air distribution through the ducts.

What you do is remove the lower section of your AC unit so that you can look up in to the bottom of your system to see how the duct is sealed. Then you get a roll of aluminum duct tape and some latex duct sealing paste at Home Depot. After you have cleaned everything and resealed the ducts, then you cover all of your tape joints with the duct sealing paste. This will prevent the tape from coming loose in the future.
While you are at it, you will find four bolts that secure your AC unit to the coach. It is a good idea to check them to see that they are SNUG, not tight, which will ensure that your gasket is compressed enough to prevent water leaks.

It wasn't a blockage for me but a terrible taping job. All of my cold air was escaping into the ceiling and going into the ductwork. I redid the tape job and all is fine.