You are definitely missing the mechanisms that Greg has shown a pic of above. I can see the telltale sign that someone has cut through the pivot bolts and has left them behind in the angled pieces that are attached to the frame. I had the exact same issue with my van when I purchased it. Someone had removed those folding mechanisms, seemingly because they interfered too much with the driver's side seatback. I was able to buy those brackets from RB Components and get my gaucho operational. In my situation, someone had actually removed the whole seatback/narrower portion of the gaucho and I had to build a completely new one. Since you already have yours, it will be a much easier project. Don't forget to buy new legs (they fold for storage) for supporting the section of the bed that is in the aisle, as the scissor brackets themselves are not strong enough to support the weight that they'll be subjected to.
Here's a link to the folding mech:
And here's the folding legs:
Let me know if you have any questions.