Fully close then re-open the app.
Double press Home button to show active apps, select channels, down button to select the little X, and center button. This actually closes apps.
If that is what you have been doing, and it still shows up as blank data, then something else wrong.
Is your Shield on wifi or wired ethernet? If wifi, then that may be the issue, try wired.
Does the server webpage Admin ui have guide data? Guide data refreshes overnight.
Also, like i said, this happens to me semi-frequently on BOTH Shield and Apple TV, so i always assumed it was normal behavior due to the devices OS suspending or sleeping apps.