I have the same problem. I think this is a more widespread problem that's related to Alfred 4 (and Big Sur possibly). I did all the steps recommended here, and after that failed, went through this list and updated Alfred (I'm now on Alfred 4), and then did another rebuilding of the index and clearing of Alfred's cache, but still I'm not seeing my applications show up in the Alfred search (before w/ Alfred 3, it seemed like it was just Zoom that wouldn't show up; now none of my installed apps show up).