Hello,
I have several sheets where I use Countifs using a referenced sheet and they were working fine until recently that now return 0. I tried remove a reference and then redo it and it still returned zero. My guess is that there is something going on with smartsheet itself. Here's an example of the countifs that used to work fine and won't:
=COUNTIFS({AC-2B_Completness}, Status@row, {BU_Completness}, BU@row, {Phase_Completness}, Phase@row)