A keyboard not typing can be due to a variety of reasons including hardware and software issues:

• Hardware issues include dirt or debris under keys, loose or damaged connection between keyboard and motherboard, or physical damage.
• Software issues may involve driver problems, settings like Sticky Keys or Filter Keys interfering, incorrect keyboard layout or language settings, or malware affecting input.
• Sometimes the keyboard can be "locked" by accidental key combinations such as Fn + Num Lock.
• External keyboard working but internal keyboard not often indicates hardware failure of the built-in keyboard.

Common troubleshooting steps:

• Check and clean dirt under the keys.
• Restart the device.
• Check connection, especially with external keyboards.
• Update, uninstall, and reinstall keyboard drivers.
• Disable accessibility features like Sticky Keys and Filter Keys.
• Verify the keyboard layout/language settings are correct.
• Try keyboard unlock shortcuts (like Fn + Num Lock).
• Use an external keyboard to isolate if issue is hardware.
• If hardware damaged or connection loose, professional repair may be needed.

These points cover most common causes and solutions for a keyboard not typing on a laptop or PC.