My understanding is that you’ll receive an email telling you that the mobile membership has now been applied to your account. As for “not working” on their mobiles, the mobile membership does NOT have all the channels as the Day/full month membership.
When did you purchase the Day membership? Has it been almost 10 days?
What you need to remember is that it’s 10 working days and not calendar days.
FYI that I do not work for NOW, just a NOW customer trying to help