2004 s 500 trunk problems
My 2006 s500 had hinges that dragged a lot and would not auto open. I used some gun oil (that's what I had) and every thing moving better. I also replaced the trunk struts as I did not know how old they were. The check I would also do is use the auto release button. Wait for the click and try to gently help it open. You should hear the lifting motor trying to open, but if not then it is time to track down the fuse and/ or check the motor at that point. It also works on a self contained hydrolic fluid system that might be low.
A youtube video on the pump I found.
im gurssing you have the pump under the battery and it had run out of hydraulic fluid or failed electrically






