Do you try to push the Reset Button and after then the Setup Button, if you push the setup button then the security access change. After then you must push again all other buttons of Adapters, to change to same security key.

If you don't push the button the Adapter can't connect to the PLC network, you try to use the Software?

Maybe the 3. Adapter it's defect... then Powerline-Shop.com replace the faulty Adapter.