What causes the car not to turn over when it is getting electrical power? on 2000 Chevrolet Cavalier

The grid cluster and all the internal and external electrical parts work but the car will not turn over, it’s dead. I have checked the battery and the starter, and both are working properly. What else could be the issue? I would greatly appreciate any help possible. Thanks for your time.

Asked by for the 2000 Chevrolet Cavalier
Is the starter working properly ON the car or off? Not understanding your use of the word 'dead' in your description.