Unable to adjust brightness on my MacBook Air M1

start by ensuring that the F1 and F2 keys are not set to function as standard function keys;

you can verify this by navigating to System Preferences > Keyboard and ensuring the option to use F1, F2, etc., as standard function keys is unchecked.

Additionally, check if the 'Slightly dim the display on battery' option is enabled by going to System Preferences > Battery > Options and unchecking it if necessary.

If the problem persists, consider restarting your MacBook and closing and reopening the lid, as some users have reported that brightness controls become responsive after this action.

It's also advisable to keep your macOS updated to the latest version, as software updates often include fixes for such issues.

If none of these steps resolve the problem, contacting Apple Support or visiting an authorized service provider may be necessary for further assistance