How did you confirm the functionality of the screen / LCD cable / SSD / RAM / keyboard / trackpad / battery / new backlight fuse? Also, have you tried a PRAM or SMC reset? If the backlight fuse had failed previously, it might've been due to a larger issue with the display logic. If you've fully confirmed the health of the other components, then my best guess is that there's a fault on the logic board somewhere, but to figure out where you'll need to investigate the related circuits on the board. Good luck!