I have the Moto 4g. I have no ringtone when calls come in. What should. I have already checked the Volume an it is as high as it goes.
Have you checked whether Do Not Disturb is turned on?
Settings | Sound & notification | (either Interruptions or Do Not Disturb).
Or maybe you set a custom ringtone that is really faint? Try setting the ringtone to a standard one.