2003 vue alarm will not change mode

[Grimace84]

I have tried to change the mode for the security system according to the manual and nothing works. It remains the same. When you get out of the car, about a minute goes by and the horn toots and the system is armed. Doors locked or unlocked, doesn’t matter. Open door and the horn starts blaring. Can’t change the mode with the key fob. I follow the directions and it beeps in acknowledgement that it worked but a minute later, it beeps the system armed and if you open the door, horn goes nuts. Very annoying. Any ideas? Thanks y’all!