Thank you both for the replies. Yes that was a typo in my post (but not in my actual formula). It looks like the issue is with the date.

EDIT

Okay I have tried a few iterations and I'm still stuck on the date. I suppose I'm just not understanding. I feel like this should work, but I'm getting buggy results:

=AND($B$5="C",D5<=(TODAY()-320),$G$5="")

After entering that conditional formula, I tested it by changing the date in cell D5 to some dates that were clearly out of range on both sides. At first it seemed to recognize the cutoff by highlighting red at the right value, but then when I changed the date to the other side of the range, the red would not go away. Any ideas? (I tried putting the arguments in alphabetical order out of curiosity, but that did not seem to make a difference).