Reading the T&C's with this offer, NowTV are saying it takes 10 days for the mobile sports pass to be added to your account.
Here's the T&C's with the offer in question.
Sky Sports Day or Week Pass plus a free 4-month Sky Sports Mobile Month Pass bundle:Available to (1) new NOW TV customers and (2) existing NOW TV customers without an active Sky Sports Day, Week or Month Pass on their account. Offer not available to existing customers who are billed by a 3rd party (e.g. via Apple, Vodafone); customers on an existing Sky Sports Mobile Month Pass offer that has more than 30 days to run; or to some Combo and NOW Broadband customers –check your eligibility here.Offer bundle entitles customers to a Sky Sports Day Pass priced at £9.98 or Sky Sports Week Pass priced at £14.98 with a free 4-month Sky Sports Mobile Month Pass. Sky Sports Day Pass lasts for 24 hours after you start watching. Sky Sports Week Pass lasts 7 days after you start watching. Your Sky Sports Day or Week Pass must be activated within 365 days of purchase. Your free Sky Sports Mobile Month Pass will be auto-applied to your NOW TV account within 10 working days of your bundle purchase, and will start as soon as it’s applied to your account. At the end of the free 4-month period, your Sky Sports Mobile Month Pass will automatically cancel. Red button and interactive services are unavailable. Sky Sports Mobile Month Pass includes Sky Sports Premier League, Action, Arena, Racing and News. Only available on compatible smartphones (see device compatibility below). To watch your Sky Sports Mobile Month Pass alongside other NOW TV Passes, at least one of the registered devices on your NOW TV account must be a compatible smartphone. You can only watch your Sky Sports Mobile Month Pass on one smartphone at a time. All live scheduling may be subject to change.