If your keyboard has a single dead key, it may be worth removing the keycap and spraying canned air to make sure there isn’t any dirt or debris causing the key to fail. A trick to remove the keycap is to use two paper clips- bend them in the shape of a hook or “J” and pull the keycap straight up) and spray canned air inside the key switch to remove any dirt/debris. If there appears to be any sticky residues on the keycap or on the key switch, try to clean the area as best as you can (usually a damp paper towel is good enough).
If the key is still not working, please contact tech support for further help.
If your keyboard has multiple dead keys, likely there is a short in the keyboard and requires a repair. Contact tech support for an RMA number.
Check keyboard connections. Make sure the keyboard is connected directly to a USB port on the computer. For testing purposes, do not use a USB hub, docking station or KVM switch. Connect direct. Reboot computer. Press the Fn key and see if the LED light turns on or not. If the light turns on, it indicates power is received. If the LED is not turning on, that indicates a physical problem with the keyboard.
You can also try connecting the keyboard to a different computer (preferably a different brand and/or model) and see if you can reproduce the problems or not.