First thing to do is to try to reseat the ribbon cable. It's pretty rare for the entire keyboard to stop working and usually it's just a few keys that fail. 

If you've never removed the keyboard before, it is pretty easy.

- Remove the power adapter and battery

- Remove the 2 screws holding the bottom cover and slide the cover off

- Locate the 5 holes marked with an I and remove these screws

- Very carefully pull up the plastic bezel that surrounds the keyboard. The clips around the hinges are usually quite tight if it has never been removed before. There is a cable that connects this bezel to the board. You can just fold the bezel up to the LCD and leave the cable plugged in.

- Remove the 5 small screws holding down the keyboard

- Pull the keyboard towards you and you will see the large flat ribbon cable. Open the connector and remove the cable. Check for damage and reinsert it, making sure that it is seated straight, and close the connector. The smaller cable is for the AlienFX lighting. 

You can check to see if it's functioning before putting it all back together but it's up to you. You can press the power button that sits under the Alien head without the Bezel being back in place. 

Hi @angelmae05 welcome to this user to user discussion forum. This is not Dell Support. 

Opening post does not say POST diagnostic is reporting hardware fault, such as keyboard test failed. Press and hold down F12 key at splash to open Boot menu. Use up and down keys to select Diagnostics and press Enter to run Dell ePSA Diagnostics. If all ePSA tests pass, its probably a software/driver problem. 

Run Windows Check Disk to look for and automatically fix any files problems on the OS(C:) boot drive. 

Visit Support for Alienware M17x R3 Drivers & Downloads to get Dell Windows 7 x64 updates. If the installed operating system is Windows 8, 8.1, 10 or 11, the Dell updates are not available. Intel Driver & Support Assistant will identify your products and get driver and software updates. 

Please click on Kudos to say thank you for response from user that is not employed by Dell. Please share an update on progress, so that other users derive benefit from your experience. Thank you. 

@XPS_Man That link is for the m15 R3 and m17 R3. The OP's post was for the M17x R3. 

There are some known issue with this Keyboard why else would there be a Firmware available for Keyboard. 

Try this 
https://www.dell.com/support/home/en-us/drivers/driversdetails?driverid=tf18w

ALIENWARE M15 R3 / M17 R3 Both use same firmware. 

@XPS_Man    

M17x R3 - 2011

m15 R3 / m17 R3 - 2020

He may mean the m17 R3 but he asked about the M17x R3. They are 9 years apart.