Can no longer share files to app

I have an iOS/iPadOS app that has the ability to open files by using the Share action in the Files app. The app receives the application:openURL:options: method, but when it tries to access the given url, it produces this error:

Error Domain=NSCocoaErrorDomain Code=257 "The file “Zippy.cbz” couldn’t be opened because you don’t have permission to view it." UserInfo={NSURL=file:///private/var/mobile/Containers/Shared/AppGroup/B1C0C77A-2E86-4BD7-9344-845D6DA6FA74/File%20Provider%20Storage/Zippy.cbz, NSFilePath=/private/var/mobile/Containers/Shared/AppGroup/B1C0C77A-2E86-4BD7-9344-845D6DA6FA74/File Provider Storage/Zippy.cbz, NSUnderlyingError=0x283c6d860 {Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"}}

This used to work in earlier versions of iPadOS. It's currently running 16.5.1 ©. I see "AppGroup" in the path. Does that mean that something thinks my app is using a shared app group? It's not. Does it need to now in order to receive a shared file?