The control voltage is not present.
Check your voltage at the start-up alarm. If 120 volt is not present, back track the voltage until you find where it stops.
Check to see if all your “Stop All Motors” buttons are pulled out.
Check whether the main circuit breaker is turned ON.
Check whether the “Control Volt” Fuse is blown.
Check to see if the contact block on the back side of the startup horn button closes when being pressed.