2000 caravan the headliners are starting to sage. What's the best way to get them to go back up and stay

 

get new ones

Is it the entire headliner coming down for just the cover fabric

 

I have not had any luck trying to keep the lining up on the hard cardboard liner. I have found that the foam attaching the cloth deteriates and almost nothing will make it stick and have it look good.

I have taken it out of the vehicle and had an upholstery shop replace the cloth covering. You just need to find a shop that will do the work.