Not able to select Key Columns

Not able to select Key Columns

Setting up tagging and key columns, but the 'OK' button remains grayed out  Can't click 'OK' to save key columns, option for "Columns with unique values for all rows (recommended)" is not available.

  This will happen when each row selected as a key column is not unique.  Add columns to data set so that each row can be uniquely identified.