computer tune no start

[g-loc]

I have a 2000 monte carlo. I sent computer out for a performance reprogram. Installed when i got it back and car won't start. Starter does not engage. All dash lights drop out when in start position on keyswitch. Dash display returns when releasing key. Notes: Battery voltage is strong with no excessive drop. Security light comes on for a momment when key is released.
Was told by shop that reprogrammed it to follow this procedure....
1)Turn key to ign positition and leave it there for 15 minutes. 2) Turn to start and release back to ign position. They said repeat procedure approx.4 to 5 times and car will start.
I've performed this 3 different times. Fortunately I have a spare battery.
Car still won't start. Symtoms have not changed..
ANY AND ALL HELP OR SUGGESTIONS WOULD BE GREATLY APPRECIATED!

One other note.. Not sure if it is relevant,but, I have an aftermarket stereo head unit. I know stock one has programming functions for various things.

[richtazz]

Have the battery tested on a machine for amperage (auto-Zone and Advance have nice testing equipment). It is very common to have 12.5-13v, but not enough amperage to turn the starter. Does it do anything when turned to start (click, hum, crank slow, make a "zing" noise)?