I just completed the campaign on coop with a friend. After the end cut scene, he got the achievements and I did not. I checked and there shows no data that I completed Maw (the last mission).
Chances are, it’s glitched and will unlock by itself within a day or so. It’s happened to me as well.
Nope, I had the same problem. We had to run through it again with me as the host and I got them.