Check you have enough internal storage on your panel. Access the quick menu by pressing the small arrows on either side of the panel.
Open settings where you will be able to access the information about the panel from the bottom icon. You will see the amount of storage available on the panel as well as the memory space. Memory is the RAM used to run the applications whereas storage is the space the applications take up.
Ensure you have formatted your USB and it is at least 8GB in size. Verify that the app is .apk format if not the file will need to be converted via an online application. Be sure that the app isn't made for a version higher than Android 8. Copy the .apk app file onto the root file of the USB. Do a hard restart of the panel by switching off and on the main power switch located on the back of the panel. If you are still unable to solve the issue please log a ticket with our support team.