UPDATE: Checked the relied valve -- it was OK. Opened up the filter and saw this:
That vertical pipe was cracked at the top as maybe you can see, and the little cap wasn't sitting in there. I applied duct tape and sealed it. That little cap seemed to have a few vent holes in it so I sat it in the pipe but not fully. Now the filter seems to work as it did before!
My new question is weather that cap is actually supposed to be sitting all the way down in the pipe, closing it off? Am I right to have it sitting out a little? What do you think?

That vertical pipe was cracked at the top as maybe you can see, and the little cap wasn't sitting in there. I applied duct tape and sealed it. That little cap seemed to have a few vent holes in it so I sat it in the pipe but not fully. Now the filter seems to work as it did before!
My new question is weather that cap is actually supposed to be sitting all the way down in the pipe, closing it off? Am I right to have it sitting out a little? What do you think?