Although you had it installed, It may not actually be meant to work with your device. From the Direct TV site....
What do I need to watch DIRECTV on my tablet?
iPad® 2, iPad® Mini and iPad® Air (iOS 8 or higher required, first generation iPad not supported)
Android tablets running OS 4.2 - 5.x (device and screen size):
Samsung Galaxy Tab 3 7.0"
Samsung Galaxy Note 10.1"
Google Nexus 7
Samsung Galaxy Tab 4 10.1"
Samsung Galaxy Tab S 10.5”
Samsung Galaxy Tab 4 7”
Samsung Galaxy Tab 4 8”
Since your device is not listed, I am not so sure it will actually work with the app.
You may need to discuss this with DIRECTV and see if there is a way to get it to work on your device.