Make sure your vacuum solenoid is getting power, via the main or throttle switches. If it is, then check for vacuum at the solenoid. If power and vacuum is ok, then check the vacuum spool valve in the solenoid, it might be dry and stuck. Be careful of the tiny screws that hold the spool valve plate on, if you loose one you are in trouble. Some WD-40 will work for lube. Also check your butterfly valve for movement.
"NICK"