Is there telephone support service available

Click on the following to find Apple Support phone number for your country: Contact Apple for support and service - Apple Support

Yes, please call AppleCare.

AppleCare Contact Info

Do you have a wireless keyboard? If you do make sure it's turned on with the switch on the back.

Also if it's a wireless with rechargeable batteries connect it with its charging cable and see if that will work.

Have you tested the keyboard with another computer to verify it's the keyboard that's causing the problem?