Check whether your Lenovo model has a backlit keyboard
Press the backlight key combination: Fn + Spacebar
Press Fn + Esc if Fn lock is enabled
Try the backlight toggle key if your model uses one of these: Fn + F5, Fn + F9, or Fn + F10
Open Lenovo Vantage and check keyboard or device settings
Update Lenovo Vantage and keyboard drivers
Enable keyboard backlight in BIOS/UEFI if the option is available
Restart the laptop after changing settings
Increase backlight brightness by pressing the backlight shortcut again if supported