Greetings, ._leslie_.
I see that the flash for the camera isn't working on your iPhone 6s after updating to iOS 11. I'm happy to help.
Get help with the camera on your iPhone, iPad, or iPod touch
Your flash isn't working
Use Control Center to test the LED flash. Turn the flashlight off and on. If the LED flash doesn't work as a flashlight, contact Apple Support.
If the flash isn’t working, or it goes off every time you take a photo, check your flash settings. Tapin the upper left of the screen to choose a different setting.
If you take extended video with the flash on, or you’re using the device in a very warm environment, you might see a message that says the flash is disabled. The message remains until your device cools down.
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Take care!
