Do you have a micro SIM? If you have cut out a normal SIM, see that the card isn't damaged and the shape of the card is right. If you have a Micro SIM, try putting it in the second slot. If it can't recognize, contact Motorola and get your phone exchanged for a new one.
If you don't want to, try contacting Motorola through the Moto Care App (Help) from your phone.