Zynga admits that the Co-op Goal is truly impossible.

The power, water and time needed to fill the orders are close to impossible by them selves. That's no news to me. However, my co-op decided to go the extra mile to get the 200 favors  and...

It turns out that this is an inbuilt feature made by Zynga. Each member in a co-op can only fill 35 orders "to ensure that all players can contribute to the Co-op Goal". When the co-op needs to fill more than 35 orders per member there is no point in playing.

Link

Note that we filled 109 orders out of 110. In our case we filled more than 35 orders each, but are still one order short of filling the goal.