Hi @Anonymous User
A forum member had a similar NowTV email offer, but it was a Cinema 3 for 1 offer deal instead of a 3 for 1 Entertainment offer.
I am not familiar with these email offers, but see if there is anything in the thread linked below can assist you in some way
https://community.nowtv.com/t5/Offers-Vouchers/Re-adding-tv-pass/m-p/523377#M6061
Won't be able to offer any further advice other than what's in the link above.
Maybe somebody on the Community Forum who has successfully applied this email offer to their account can help you further if nothing in the linked thread above works.
