My ROG phone 5s' flashlight stopped working

Hi,

You may have to perform the factory reset just to prove whether it's a software or a hardware problem.

Back up the phone to the cloud or a computer before doing the reset, then reset the phone and check if the flash works OK or not after the reset.

If not it's a hardware problem.

If it works OK (or even if it doesn't) you can restore the phone to what it was before the reset by using the restore data setting in the phone and the backup you created.

If it worked OK after the reset check that it is still working after you've restored the phone using the backup.

Note: If there's a Google account associated with the phone, you will need to know the User ID and Password for the account to access the phone once the reset has been done and you set up the phone again. This is due to the FRP lock (factory reset protection) being enabled by the reset.