1 simple, fast suggestion. Although the truck divider (Curtain) may be in place, it might not be correctly engaged in the bracket on the driver's side. The Left side has a top switch incorporated into the bracket. This happened to me, I changed the bracket, and it started working.
While there, check to see if the bracket is in one piece, sometimes they crack and when they do, the divider and the switch will not correctly engage. YOU WILL NEED TO REMOVE THE LINER ON THE DRIVERS SIDE IN THE TRUNK

If you don't already have a spare (impossible to find) set of trunk divider brackets, they can be purchased (Reproductions) here on the site, I believe it's forum member Shamrock. I purchased a set. great quality worth every penny

YOU CANNOT LOCATE THESE USED ANYWHERE UNLESS YOU'RE THE FIRST GUY TO COME ACROSS IT AT A BREAKER YARD.

Please keep us posted on the developments. If it's the bracket, PLEASE let us know.

Wishing you success in correcting your issue.