Take a cable off your battery and from a separate fully charged battery hook jumper cables into the circuit, one to the connected batt terminal and one to the disconnected cable end. Remember to pay attention to the pos ground if so equipped. Then try it. Your alternatives do not exhaust the universe, though. Could be a ground( batt to body, body to frame, engine to frame). Bad solenoid, bad power connection somewhere in the cables to starter. You can isolate these by connecting your earth jumper cable direct to a clean spot on the engine block and the power cable to the solenoid output.
Bob