If you have or are reconfirming your eligibility code online with HMRC there is an error on their system about childcare vouchers.  

Parents can claim both 30 hours and childcare vouchers.  Unfortunately HMRC system is showing an error message saying that you can only reconfirm once you've stopped your childcare vouchers.  This is an error and HMRC are working to fix the problem, in the meantime parents who see this message should call HMRC helpline on 0300 123 4097 straightaway so that they can help you with your application.  

See scheme information for more details.