1999 Chevy Van Ignition Switch

Try this first to relearn it, Insure the ignition key is in the ON position.
Insure all passlock TM module and VCM/PCM DTCs have been cleared.
Momentarily rotate the ignition key to the CRANK position (Do NOT start the vehicle), then release it to the RUN position (Do NOT key OFF in the process).
Wait 10 minutes. Observe the SECURITY indicator. Refer to the following list for the appropriate responses:
If the passlock TM sensor was replaced the SECURITY indicator will flash for the 10 minutes duration.
If the passlock TM module was replaced, the SECURITY indicator will flash for a few seconds and then remain ON for the remainder of the 10 minutes duration.
If the VCM/PCM was replaced with a new programmed VCM/PCM and connected to the vehicle for the first time, the vehicle will Start and this procedure may not be necessary.
If the replacement VCM/PCM was connected to any vehicle at any other time, even momentarily, the SECURITY indicator will flash for a few seconds and then remain ON for the 10 minutes duration.
The SECURITY indicator will transition from flashing to ON briefly to OFF after 10 minutes if remaining in the ignition ON position.
Turn the ignition switch to the OFF position and wait for 10 seconds.
Repeat steps 3-6 two more times. The new security code is ready to be communicated among the Passlock sensor, Passlock module and VCM/PCM. The new password is learned on the next ignition lock cylinder cycle from OFF to CRANK to ON (start attempt). Post back if this works.

I would scan it for any theft codes, it would be a good starting point. When the ignition got damaged, there might be more damage somewhere else that you didnt see, I would double check to make sure everything is connected. Also the passlock sensor itself could be damaged also. Is the security light on or flashing?