Are there any lights on the ESC ????
I'd check it's plugged in properly to the right slot on the RX, I'd try another ESC if you've got one with that motor and another motor with that ESC.
The ESC may have a protector to stop it starting the motor if there's any throttle input so check the trim tabs at zero nad the throttles at the bottom when connecting the battery, can you reverse the servo on your TX on the throttle channel but make sure you switch it back again if it's not that and check all the wiring especially if you soldered bullet connectors on etc.