Are you wanting to move the App? or just move the Videos? If you are trying to move the app to the SD card, well then that will only work if you are running "Marshmallow". Otherwise you won't be able to move and run apps from the card. If you are running "Marshmallow", make sure you start with a blank card. Why? Because when it is made "Internal" storage rather than the standard "External" storage the card will be formatted, wiping anything that was already on it, and also encoded so that it is it only readable by that device.
How to turn external SD card into internal storage on "Marshmallow".
1. Go to device “Settings”, then select “Storage”.
2. Select your "SD Card", then tap the “three-dot menu“ (top-right), now select “Settings” from in there.
3. Now select “Format as internal”, and then “Erase & Format”.
4. Your SD Card will now be formatted as internal storage.
5. Reboot your tablet.
NOTE: If you don't reboot the tablet, many things may not work correctly, so make sure you do.