My Asus laptop also runs into the same issue after installed the October update. * After it boots up, return to attach the keyboard again. Adjusting the brightness level doesn’t apply quickly, because you need to reboot the system. * Under the Brightness and color heading, manually move the slider of Change brightness to the right side. * Open the Settings app from Start menu, go to System > Display. * First detach the keyboard from your Surface Go or Surface Book.
If your device is plugged in to the official charger for a while and then unplugged, the Surface logo becomes plenty bright during the pre-booting process and then the brightness will dim by itself.
