Garmin Fenix 5x backlight is not working? Here is the solution : Setting > System > Do Not Disturb > Status : Off. Done! Now go try turn on the backlight should works. Here is step by step guidance for the solution :
1) Hold the middle button on left side for 2 seconds.
2) press bottom button on left side to find "Setting".
3) press top button on right side to go into the "Setting" page.
4) press bottom button on left side to find "System".
5) press top button on right side to go into the "System" page.
4) press bottom button on left side to find "Do Not Disturb".
6) press top button on right side to go into the "Do Not Disturb" page.
7) press top button on right side to set "Status : Off".
8) press bottom button on right side for many times until you are back back back to the main page of your watch.
9) Test to turn on your backlight now. Should works now.

Why this problem happen? It is because when u connect your watch to computer for charging battery of ur watch, your computer will auto set on "Do Not Disturb", so u need to repeat the 9 steps to turn it off again.