Since we need the keyboard for doing any kind of work in the laptop, when it stops functioning, performing things on the it becomes a big hassle.  If your dell laptop keyboard stopped working, try these troubleshooting steps and who knows it might either fix it or give you a fair idea of the problem. Before you proceed further, if you are planning to try out the disassembling  step make sure you follow adequate safety measures by wearing rubber gloves and removing the power cord and battery before performing any parts removal process.
1. First check if all the keys or few of them are not responding. You can also try restarting the system again as it might also be due to the computer freezing or software not responding. If none of the keys are working, confirm that the Number Lock and Caps Lock LEDS are lit. If you have a spare USB keyboard, try connecting it and check.. If it responds, the onboard keyboard is the cause. If it doesn't, then definitely there is a problem with one of the components or settings in the laptop and at this point, zeroing in the laptop keyboard as the cause of the issue is not recommended.

2. In certain cases, due to rough handling of the laptop, it might cause some disconnections of cables. So this step is recommended to make sure that the connectivity is fine. Most Dell laptops have easy steps to remove the keyboard. You just have to get a flat head screw driver and use it to pry open the hinge cover at the notch on the right side below the LCD screen. Once it is done, find the screws that hold the keyboard and remove them. Gently pull the keyboard towards the screen and disconnect the cable attached beneath the keyboard to the circuit board. Reconnect it again, put back together the components and start up the system to check.
3. In cases where only few keys are not responding, check if those keys are worn out or displaced. It they are then you have to get the whole keyboard replaced as individual keys are not available. If the keys look fine, confirm whether you might have activated the sticky, toggle or filter keys activated. You can deactivate them back from the ease of access centre or by pressing the shift key for 15 seconds until you get the pop-up window to disable it.

4. Find out whether you have downloaded or installed any software as viruses and other malicious files can also cause the problem to occur. You can run an antivirus scan and perform a system restore. Also check in safe mode to make sure the hardware is working fine.  In some Dell laptop keyboards, the numbers and letters are placed in the same key so you have to verify if the Number Lock keys are on or off.

The most important thing here is to verify the roost cause as to whether it is a software or hardware issue. This is because if it is a software issue and you get the keyboard replaced, you will still face the same issue again. For those who have hardware warranties in their Dell laptops, you can get it replaced while those who don’t can get it repaired or replaced at a computer repair centre or buy a laptop keyboard of the same model and install it on your own if you are technically savvy.