You could use the Pervasive Control Center to run a SQL query or two...
starting with
SELECT bkic_prod_code FROM BKICMSTR WHERE bkic_prod_txble = 'N'#
which would give you a list of all items with this setting set to no. Mine reported "(13527 row(s) affected)"
You could then run
UPDATE BKICMSTR SET bkic_prod_txble = 'Y'#
which would set them all to yes.
Easy peasy