If the requirement is that the ground rod has to be driven in, last 2 or 3 inches, tap with hammer.
When I installed a new electrical panel and service, we, the licensed electrician and I, drove in one new ground rod and used the old ground rod. The house sits on hard pan and the bed rock is about 12 to 18 inches below the walk out basement floor. We hit the bed rock, electrician said that was good, would meet code.