Two table update just isn't working in MySQL. No updates!

First the wide code.
I included a select that confirms the fields are set.  With / without the table qualifier doesn't make a difference, so it appears.

UPDATE   zModem_Census     z
     ,   ModemConfig       mc
   SET   z.have_plan_rates_set = 
           ( CASE WHEN NOT ISNULL(`mc`.`intl_rate_plan_id`)   AND NOT `mc`.`intl_rate_plan_id`=''   AND NOT `mc`.`intl_rate_plan_id`   = 'Unassigned' THEN 1 ELSE 0 END 
         AND CASE WHEN NOT ISNULL(`mc`.`dom_rate_plan_id`)    AND NOT `mc`.`dom_rate_plan_id`=''    AND NOT `mc`.`dom_rate_plan_id`    = 'Unassigned' THEN 1 ELSE 0 END )
  WHERE  z.modem_config_id = mc.modem_config_id
    AND  z.posting_period = 'Aug 2016'  ;

SELECT (CASE WHEN NOT ISNULL(`intl_rate_plan_id`)   AND NOT `intl_rate_plan_id`=''   AND NOT `intl_rate_plan_id`   = 'Unassigned' THEN 1 ELSE 0 END 
         AND CASE WHEN NOT ISNULL(`dom_rate_plan_id`)    AND NOT `dom_rate_plan_id`=''    AND NOT `dom_rate_plan_id`    = 'Unassigned' THEN 1 ELSE 0 END) AS HaveSet
FROM ModemConfig  ;

Select allOpen in new window

I've also (originally) tried using JOIN syntax:

  UPDATE zModem_Census     z
  JOIN   ModemConfig       mc
    ON   z.modem_config_id = mc.modem_config_id
   SET   have_plan_rates_set = 
             CASE WHEN NOT ISNULL(`intl_rate_plan_id`)   AND NOT `intl_rate_plan_id`=''   AND NOT `intl_rate_plan_id`   = 'Unassigned' THEN 1 ELSE 0 END 
         AND CASE WHEN NOT ISNULL(`dom_rate_plan_id`)    AND NOT `dom_rate_plan_id`=''    AND NOT `dom_rate_plan_id`    = 'Unassigned' THEN 1 ELSE 0 END
  WHERE  z.posting_period = var_posting_period  ;
  COMMIT ;

Select allOpen in new window

Parentheses don't seem to make a difference either.
What am I missing here?

Thanks!