If you are experiencing frequent disconnects between the Pac-12 Now app and Chromecast, please first check the Apple app store or Google Play for Android to make sure you have the latest version of the Pac-12 Now app. Having the latest version will ensure the best possible experience.
If the latest version does not solve the issue, you may need to reset your Chromecast.
You can reset your Chromecast by turning off the Chromecast and unplugging it from it's power source.
If issues still persist, you may need to restore your Chromecast to factory settings. Instructions to do so from Google are provided here: How to Factory Data Reset (FDR) your Chromecast.