@Anonymous User
Welcome to the forum. The usual cause of this is misreading the code on the voucher, have you tried a few different combinations, especially where a letter may be a number or vice versa, e.g 5(five) and S, 1 (one) and I (capital i ), 0 (zero) and O (capital o) etc?
The following help page gives more info
http://https://help.nowtv.com/article/voucher-code-not-working
and if you are still stuck after all that, go to
https://help.nowtv.com/contact-us/voucher-code-not-working
and choose the option for live chat who can check the code for you.
