Hossein,
Faulty starter or starter relay. Make sure lift is in neutral. Lift needs to see park brake engaged. Make sure PB switch is working. Possible key switch has failed. Verify power going to solenoid at starter when switch is engaged. Loose cable connections or bad ground can cause this issue. Good Luck.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.