This problem has been reported many times over the years
All users codes are not accepted. The code is reset back to 1234.
This is possibly due to the Function Key F#.
The default setting is to go to Answering Machine Menu
It will ask for the user code. After entering the user code, the menu is
"0 to Erase Mailboxes
1 to Add User
2 to Erase User"
If you select 0, then all user codes and messages are erased and the user code defaults back to 1234
This probably happens when the user is in a hurry to disarm after an alarm, and they press F#, then they enter their code and press 0
If a user says they have lost their code, 1234 may work
We shall remove this Function Key in the defaults
It is advisable to make the change using Comfigurator for existing systems