Thanx, Nevada! You are right, I forgot that car has an after market security control.
It was a major pain in the backside when I bought the car (used) so I removed the battery from the remote and threw it in the glove box 'cause I didn’t want to fool with it any more. I put the battery back in the remote and pressed the disarm button - fixed the alarm issue.
I was convinced the alarm horn was installed by GM because when I removed that horn (to fill the thing with caulking) there was a sticker under it saying “Do not remove” with the GM logo on it.
Note to self; if I ever need to disconnect the car battery again I’ll need to dig out that remote, again.