viper 5901 replaced battery, crank but no start

[CTScott]

You have a second module along with the Viper to do the immobilizer bypass. It sounds like that module lost its configuration. If you can find out which one was used you should be able to find the manual for reteaching it the key data (which typically involves a bit of aerobics with some combination of inserting and removing the key, tapping on the brake pedal, etc.)