Hii..
I had this issue with my moto g 3 after i got the usb charging flex changed.No sound from phone speaker.
I went through some answers here.Tried to press just above the usb flex cover after opening back plastic cover of the phone and the sound is working. Relieved.. i guess the speaker circuit is near that and it gets loose.. happy that its working.. temperory have added a piece of paper for extra pressure inside the cover... Hope it helps... :)