I know it's seems frustrating when laptop's Touchpad stops working. But don't worry, I will show you some simple steps to get your touchpad back to life again.
Try Restarting your Laptop. Sometimes there is only a minor issue causing your touchpad not to work. A simple "restart" can solve the touchpad problem in no time.
Check if your laptop is Frozen or Crashed. Press Windows key and then Ctrl+Alt+Del to see if it's responding or not. On Mac, Press Cmd+Space to do this same Oparation.
Some Laptops have a Feature where you can disable your laptop's Touchpad with a key combination like (Fn+F6 or Fn+F8). Same Key combination also can turn "ON" your Touchpad again.
Try removing External Mouse (Wireless Mouse too) to activate the Touchpad, because some Laptops don't allow two input methods at the same time. So the Touchpad goes turned OFF.
Go to Windows/Mac Settings and review Touchpad-related settings to see if everything is good there. Make sure your touchpad is "ON" and has permission to click and track.
If your Touchpad Driver is broken or too old, it can stop working. Check your Device Manager to ensure there are no errors, and ensure that your drivers are updated to the latest version.
Laptop Touchpad can be Disabled in BIOS/UEFI. Almost every Laptop has this feature. You should review your BIOS/UEFI and make sure your laptops Touchpad wasn't Disabled there.
There is a Feature in multi-purpose laptops like Tablet PCs that disables Touchpad when you’re in Tablet mode. Try disabling this feature and see if your laptop's Touchpad goes live again.
Those simple methods should solve all of the common problems related to Laptop Touchpad. If still your laptop Touchpad not working, there could be a Hardware Issue, you need to take your laptop to a Service Center.