Try this from the roof with the slide in, maybe out a half foot.
Pull the topper material up and toward the middle of the mh, probably easer with 2 people if it's a big slide.
Pull till you can see the slot that the topper attaches to. Now lock the roller in place, try a Phillip's head screwdriver in the slot opposite end of the roller.
Try pushing the cord, moving the topper around will help.
Could be a lot of pull out 1", push in 1 1/2", etc, etc...
After replacing our awning fabric I figured out the trick???
More if this doesn't work