Below are some helpful tips to check before troubleshooting further:

1. Check the brightness level on your laptop. It may be set to the minimum brightness.
2. Check if any keys on your laptop’s keyboard are stuck, preventing the correct display brightness.
3. Reset the laptop’s display settings.
4. Check the display settings of the external device (if used).
5. Check the brightness in the operating system.
6. Check any energy saving settings.
7. Restart the laptop.