A couple things to try:
Clear the keypad by entering a user code, you may have to do this twice. If that doesn’t work, press the * key and see if the message goes away. The trouble may be latched in and you just need to manually clear it.
Another thing to do is perform a manual battery test. This is on Page 25 of the USER manual but the process is as follows:
1. Press the ELK key and enter a Master User Code.
2. Press the UP arrow key to find: “8-System Settings.”
3. To select this menu press the RIGHT arrow key.
4. Press the UP arrow key to find “84-System Test”.
5. To select this menu press the RIGHT arrow key. The Keypad will
display “1:Battery Test”.
6. To start the test press the RIGHT arrow key. The battery voltage and
current (amperage consumed by the system) will be displayed. The
battery is OK if it maintains a voltage above 12.2V for the test duration.