Rare option on W210 but standard on W211.
Seems your limit switch in upper position is not catching, that is why cover is not going down.
On W211 there is magnet on the cover bar that activate switch behind the panel.
Other option might be mechanical limit switch.

 

I don't think the cargo cover is Powered on the W210.

 

Can you post pics? My cargo cover is not powered.

 

I think that's what he means, the self retracting function of the cargo cover.

 

Yes. This is what I'm talking about. There is a track with a cable that's supposed to push the cover down but I have no idea how it's supposed to work or how to activate it. Is there a fuse or button for it?

 

It is not powered...you must pull it back down when you are finished doing what you are doing. It is merely a handy place to have it...in the older cars you had to retract it to put things in the load area...bigger than a small box.

 

I guess this really was a rare option for the W210. I can see some type of piston and a metal pushrod connected to it. I'm pretty sure it's supposed to be powered. I'm going to take it apart and trace where it goes and take pics.

 

I've been trying for an hour to upload pics but I can't for some reason. So I just posted on mbworld. Here is a link to the thread I stared over there with pics:

Does anyone know how this power cargo cover works on the wagon? - MBWorld.org Forums

 

Looks like mine...but I've never seen the "push rod". There is a cover above each side window...pull it down and see if there's anything in there.

 

To get picture downloading privileges you need to have a number of posts. I think it was 20, but I meet it long time ago.
The pictures at MBw are downloading for 5 minutes already.
This better be good

 

You need better broadband!!

The pictures show what I have. I'm not sure it is a push rod...but would be interesting if I was proved wrong.

 

I don't have W210 wagon anywhere around, but took a look at the mechanism on W211.
The plastic tracks for the bar, do have slots with cables behind, what gives power to the button pushing cover rod.
Don't see such slot on the linked pictures, so if it is power cover, it has different design

 

2004 e320 wagon: Mine used to roll up when i opened hatch (rear) and roll down when i closed hatch. But it stopped working at some point. I hate that it doesn't function any more. Local independent mb mechanic with zillions of years experience didnt believe me when i told him how it functions. Hahahaha