I'm not familiar with your MH, but if the pull down shade is like a normal window shade and is easily removed like a residential window shade you might try this:
Pull the shade down partway, remove it and manually roll it back up. After rolling it up, return it to the sockets and try pulling it down and see if it retracts by itself. If the tension is still not enough, try repeating the procedure again. If the tension is too strong, do the opposite.
I hope this helps. Good Luck!