At some point Apple added an update where you cannot access the Photo Library on unsigned apps.
Photo Library Access
1. Use a valid Bundle Identifier on your app and then create an identifier with the same string in your Apple Developer Account (i.e com.mycompany.myapp)
https://developer.apple.com/account/resources/identifiers/list
2. Create an app on AppStore Connect using the Bundle Identifier
https://appstoreconnect.apple.com
3. Add the following properties to the Info.plist along with a brief description:
Privacy - Photo Library Usage Description
Privacy - Photo Library Additions Usage Description
4. Add a valid app icon to your Assets/AppIcon
Note:
Without following all of these steps, you will always be denied Photo Library access.