Using Keynote as virtual background failing - "Keynote not installed" message

Several others have posted about this but there have been no replies yet so I'm boosting here!

Trying to use virtual background using a Keynote slideshow; I have Keynote installed of course, that's how I'm playing it.

When I try to use the advanced feature, I get the error message (see screenshot) that "Unable to load XYZ.key because Keynote is not installed."

I tried with a .ppt file and same error message for "Powerpoint is not installed."

I tried to see if Zoom has an app for Powerpoint or Keynote; they do not.

Others are using this great feature, and I'd love to, but am stuck.

(I uninstalled, fully, the Zoom app and reinstalled; same issue)

(Computer and Zoom all 100% up to date)

(Running 2021 MacBook Pro M1 with Ventura))