cobra 3995 remote fob not working?

my van has a cobra 3995 fitter,i have just yesterday put a new battery in the remote fob as it started not to light the led red light on the fob and not switch the alarm on/off.problem is the battery now works the fob and led light,but its not interacting with the alarm and doesnt switch it on or off.Is there a procedure to follow when a new battery is installed to get the remote fob to acknowedge the alarm
Thanks
Gene