i have a 2001 chevy blazer when i hold the lock/unlock button it doesnt do anything

 

Mine as well. I had to change my battery today, and when I tried to resync it, the lock/unlock on the remote for 15 seconds doesn't do anything.

I then tried the whole door button, ignition on/off twice, release door button, and there is never any cycle of the door locks. This was all working before I changed the battery. I on;y changed it because the range was getting to where I had to be next to the Blazer.