It may be off. Fn + F12 to toggle through Off and the 2 brightness settings. Once you set it to ON it should come on when you touch a key or the track pad.
** If my response helps, please click on Like (Heart). If I resolved your issue also please click on Accept as a Solution so that others can benefit.
Bill --- Galaxy S21 Ultra 512g(VZW), Galaxy Book (original, VZW), Tab S8 Ultra, Tab S4, Galaxy Watch3 (VZW)
