Most of the time it's a hardware issue when it comes with keyboard problems. Here are some troubleshooting steps that may help in solving the issue.
- Start by uninstalling/reinstalling the keyboard driver.
- Go to Device Manager and uninstall the Keyboard driver.
- Reboot your laptop once the driver has been uninstalled and it should reinstall automatically.
- Once rebooted do test it again and see if the same problem will persist or not.
- If it does, open Onscreen keyboard then test weather or not CTRL key will work or not.
- If it does work that means it's a hardware problem, do also try it using an external USB keyboard and see if it will work or not.
- Your last option would be to replace the keyboard itself unfortunately.