If you are sure you have opened any privacy shutter that may exist on your webcam, open the Settings app in Windows.
Go to Bluetooth and Devices - Camera.
Click the 'Integrated Camera' setting.
In there, you can adjust settings on your webcam like Brightness, Contrast, Saturation.. etc. to try to improve the image on your webcam.
If that does not resolve the problem, laptop webcams are not very sensitive, you indicate you are using a room light, in that case, you need to be facing the light, i.e. the light in your room needs to be behind the laptop screen, not behind you.