Won't start everything works won't send signal to starter what to do?

If your vehicle won't start but everything else appears to work, first check the battery connections to ensure they're clean and tight. Next, inspect the ignition switch and neutral safety switch, as either could prevent the starter from receiving a signal. If those components are functioning, consider testing the starter relay and fuses. If you're still having trouble, it may be best to consult a professional mechanic for further diagnosis.