Hi @Anonymous User
Have you tried watching the Day Sports Pass on your phone first, then stop the stream, exit the stream back to the main home screen of the App.
Then jump over to your main playback device which should then trigger it on your television (assuming you are not referring to the free Mobile Pass that comes with a Day Sports Pass purchase where you can't watch on your television and need to stick with your smartphone).
I am assuming you are referring to the activation of the Day Sports Membership (see this link below).
https://help.nowtv.com/article/can-not-activate-sports-day-membership