First of all: make sure there's no update of the App available in the Google TV Play Store. If you're still experiencing issues after that, continue reading.
If the TV is already linked to a match and depending on the settings, it could be that the TV does receive a new request, but ignores it. You can check the setting "When linked, force linking to other match". If that setting is checked and still nothing works, follow the steps below.
The App is depending on some Google services to receive matchupdates. Sometimes the TV App is using the incorrect Google key to register itself. Although investigation is ongoing to solve this permanently, the only workaround possible to fix this is to clear the data of the App in the settings of the TV.
To do this one has to go to "Settings" -> "Apps" -> "Whistle"
Perform the following actions:
- Force stop
- Clear cache
- Clear data
- Open
Also check your internet connection, since the App is depending on it. After that, all should be working fine. If not, please let us know.