Why is front camera not working

First you need to find out if it's a software or hardware issue. Start FaceTime or any other video chatting app and try to make a video call to a friend of yours. Check both iPhone cameras. If they work fine during the video call, you can be happy – it’s a software issue you can easily fix (fallow the next steps below). If you can't switch or see black screen it's a bigger problem with the hardware.

Next force the camera app to close by tapping the home button twice and swiping up to close the camera app and all other programs. If it still not fix fallow next step

Next Reset iPhone Go to Settings > General > Reset > Reset All Settings. It will return your iPhone to the default fabric settings. (No data or media will be deleted) if it still not fix fallow the next step

Next Restart your iPhone Press the Home and Power/Sleep buttons simultaneously and wait for the Apple logo to appear. Let both buttons go at the same time and your iPhone will restart. Your personal data won’t be affected. Check the Camera app after that. If still not fix fallow next step

Next 'Set Up iPhone Like New' Here is another step to try in case nothing of the previous ones worked for you. Some users found out that the Camera app issue is caused by an old backup they restored. If you have the same problem, you may try to erase your iPhone and set it up as new.

Note that all the data from your device, including songs, videos, contacts, photos, etc will be removed. So if you don’t want to lose your precious data, make a backup to iCloud.

To reboot your iPhone, Settings > General > Reset > Erase All Content and Settings.

I hope this helps you.