What nowtv playback device are using ?
The only advice that i can suggest is to go to the nowtv website with your internet browser and sign into your account and click on My Account > My Passes to double check it's shown active ready to use.
Then if it shows that the one day sports pass is purchased and ready to start, log out of your playback device and then re sign back in with the exact account details you used to double check your pass on the nowtv website and then click on any of the live sports channels to see if it works.
Sounds to me you have logged into the wrong account on both your playback device and checking the nowtv website.
Have you ever created more than one username / email address in the past ?
If so check them all, if not have a word with live chat by opening the link page below and click on the drop down arrow below Anything else which should show the live chat button.