The gas and liquid posts are different, I've noticed that when I swap them I have all kinds of problems getting the disconnects on...maybe yours are swapped?
Does co2 come out when you lift the relief valve?
fwiw I use a french press most days...I use a blade grinder as well. I put a small piece of cheese cloth in the opening of the french press, it filters out everything but the delicious coffee.
It takes more than that to ruin a beer. I'm sure most of us have done it at some point without any problems. Be sure to set a bottle aside to taste a couple months down the road you'll be glad you did!
Cheers!