With pairs 1, 2, 3, and 6 correctly terminated, but pairs 4, 5, 7, and 8 not showing connectivity, the issue lies with half of the cable's wiring, indicating a possible open or short in the cable or a miswired connector. The best action is to re-terminate the affected pairs (4, 5, 7, and 8) to ensure they are correctly wired and seated. Simply choosing a different cable would not resolve the issue if the problem is systematic with the installation process. Testing other components wouldn't address the direct issue at hand, that the cable is not showing full connectivity for all pairs, and a punchdown tool is used for terminating wires into patch panels or keystone jacks, not for re-terminating cables.