Disco won't start

My 98 Disco won't start or turn over. It makes no noise at all when I try to start it. I checked the battery with a voltmeter. Looks good with 12v. I checked the fuel pump in the rear area and could hear it run when I had my wife turn the ignition. Sounded like it was running fine. So I had it towed to a Firestone to put a new Starter in the vehicle. After two new starters from Atlantic British, each starter will not engage the flywheel to turn the engine.

Is it the tech at Firestone, possibly two bad starters, bad solenoids on the starters, or what? Secondly, should I buy the Starter from a LandRover dealer or keep trying through Atlantic British ($560 at dealer vs $170 Atlantic British).

Thanks for any help!