When using the QR code to scan from an app, users may receive a black screen instead of the prompt:
<App_Name> Would Like to Access the Camera
When the above prompt does not appear, a black screen is shown instead. This happens when the app is not able to access the camera when the button to scan a QR code within the app is clicked. The app may have an outdated code or needs to be re-installed.
This article provides the steps (and an alternate solution) to resolve this issue.
Note: This affects iOS versions only.
Update and republish the app according to the detailed instructions found in the above article.
If the app is published to the latest code release, the app needs to be uninstalled and re-installed from the App Store on the mobile device.
If the above fails to work, it may be directly related to the device or iOS software and not the app. You may need to enable access to the camera on the mobile device manually.
On your mobile device, go to Settings > Privacy.
Tap on Camera to see which apps have access to it.
Scroll through the list to locate the app that you need to allow permission to access the camera, and use the toggle switch to enable access.