I also had problems with the voucher being accepted. I ended up calling customer services who I had to send a screenshot of the voucher to. They then deducted the £20 from their end.
Postcode lottery or wot
As per usual, Difficult to get the asda codes to work even in them postcodes.
Im having problems with this voucher aswell, and I meet all the criteria. Help!!
Are you having it delivered to one of the postcodes in the description