If you have a meter, I would probe the terminals in the PDC relay socket for ~12 volts with the key turned to Start.
If there is voltage at the relay, probe at the starter and solenoid with key at Start.
If no voltage at all at the relay, NSS or ignition switch is suspect.
Check connections for cables at battery and starter (not just visually) as suggested by foreveryoung001, particularly if you have low voltage with any of these tests. Having voltage present does not guarantee good connections and adequate amps, but it is at least a start.
Ultimate way to initially check NSS is to hold key in Start position while moving shifter back and forth between Park and Neutral several times. None of these actions (including having reverse lights working) absolutely guarantees that the NSS is good.
Perhaps you have performed some or all of these checks all ready. Let us know results.