The 99 MY had easy sync which is just to put the key in the ignition switch...the Coil in the ignition barrell excites the fob and the fob sends a signal to the RF receiver, the BeCM then issues a new sync code back to the key....
Only things that will stop the sync, is a duff RF receiver or the BeCM has gone into a Alarmed state....
Mozz Smith can usually get good results, send him a PM....Rick-the-Pick is the BeCM genius...a quick message to him may help too....
First check....when you put the key in the ignition barrell, does the red LED flash on the fob??
Second Check....make sure the blue aerial lead is connected to the RF receiver under the plastic trim behind the drivers sdie rear seat under the quarter light....
If they check out, get in touch with Mozz and/or Rick