Hi @Anonymous User
Any error message or code on the Stick that doesn't work on the television that it won't run on ?
Out of curiosity the NowTV Stick that doesn't work is it on the furthest television away from your Router and if so it could be a WiFi coverage issue.
If you go into the Stick Settings under Network, what's the wifi reception like ?
What happens if you swap the Stick over on the two televisions, does the Stick that doesn't work still happen or works (if you have two Sticks available) ?
Perhaps try the trouble shooting steps in this linked guide article below.