The first thing I would do is plug the scanner into a different car to make sure it works. Then check the fuses #26 and #11 which power the ALDL. Here is a guide to help you run a test and the wiring diagrams so you can see how it works:
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.