@Anonymous User
Welcome to the forum.
The usual cause of this is misreading the code on the voucher. Have a look at the following article and try 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 ), O (capital o) and 0 (zero) etc
http://help.nowtv.com/article/Code-not-valid
If you are still stuck, click the green Contact Us at the bottom left of that page and on the following page choose the option to Use Live Chat who can check the code for you.
Hi @Anonymous User
Thanks for posting, sorry to hear you've had issues trying to apply a voucher. I will need to look into your account and I'll send you an e-mail.
Please keep an eye out on your account.
Cheers
Ranj
NOW TV Team