I would trouble shoot the battery and starter first.
1. I would take jumper cables directly to the starter to see if it will engage. If not, check battery; try a known good battery. If battery good, pull starter and take to shop and have tested. Bad, buy new starter.
2. If that works, I'd take some power to the soloniod and see if it engages. If not, buy new solonoid.
3. If that works, start checking your ingition switch and wire back to same.
Hope this helps.
2004 Rubicon, 6" lift, 35s, winch, hard top, full doors, bumpers, tire carrier and rock sliders.