Suddenly will not do anything

Drove it to get a exhaust repair and got there, turned it off, within 2 minutes tried to start it again to put on ramps and nothing. Lights come on but doesn't do anything, security light blinking. Had it for 3 years and it's never happened before. Towed it to dealer, they supposedly done a diagnostic on it. They charged us $120.00. And said it's the starter. Took the starter off to go get another one at O'Reilly's. They tested the starter and said the starter is good. We checked the fuses, tried pulling the anti theft fuse out, tried jumping it off, made sure battery connections are clean and connected good, tried putting it in gear then back to park several times, even tried to reset the alarm by instructions found online using one key, don't know what else to do. Does anyone have any ideas we could try?