Keypad stopped working

My Utec ultraloq keypad stopped working all of the sudden… I could lock and unlock using the app, but they keys on the keypad would not work. They would not even light up when pressing them.
They started working again after locking and unlocking several times via the app.

What causes the keypad to stop working and how to fix it? My guests and housekeeper don’t use the mobile app - they only use the keypad to get in.