You will may run into this problem if you are getting automatically logged into Cox as a result of being on your Home Network / Wifi, but you need to log in with a specific Cox username/password in Pac-12 Now in order to have an account that has Pac-12 Networks access. Please try the following steps to work around this issue.
1) Force close the Pac-12 Now App out of memory
-for iOS https://support.apple.com/en-us/HT201330
-for Android http://www.dummies.com/how-to/content/how-to-force-close-an-app-on-an-android-phone.html
2) Turn off wifi on your device
3) Launch Pac-12 Now
3) Tap the Gear icon in the upper right
4) If you are already signed in as Cox, tap "Sign Out" under TV Provider.
5) Tap Sign In
6) Choose Cox then sign in with your username/password that has Pac-12 Networks associated with it
7) Rejoin wifi so that you don't use up your LTE data plan