This issue ended up being a bug in Xano where the dbTable variable needed to be refreshed (even though I only ever had one table in my Xano account). I typed in some dummy text and forced the Xano drop-down to search for a dbTable with that name. It didn’t find it (because there was only 1 table - the table that was previously selected)… I then reselected the only table in my Xano account - and published the API workflow - and it worked.
Thanks to @Alexis for the suggestion in this post: Google auth via Xano (through modal) issues - #21 by Alexis for this idea.