Either you accidentally changed the installer code without knowing it or you pressed (*98) the last time you tried exiting the programming menu instead of (*99). Always enter (*99) when exiting programming on your Honeywell alarm keypad.
To access the programming mode from here, you must disconnect the Vista 20P's A/C transformer plug, then remove the red and black leads from the backup battery. Wait 15 seconds before reconnecting the battery and A/C transformer plug, in that order. While the system is booting up (in the first 60 seconds), press and hold (*) and (#). The number (20) will be displayed. You are now in programming mode.
