Agree, I have the same issue WeakReference is null. It is null for all three arguments:

requiresPermission: WeakReference<Fun>,
onPermissionDenied: WeakReference<Fun>?,
onNeverAskAgain: WeakReference<Fun>?

It can be reproduced on Android < 10. For example, in my case, I have used an Android 7.1.1 build on Emulator.

I can also reproduce it on Android > 10. The references are null and so going back and forth the callbacks are not invoked.

I'm able to reproduce the problem using ktx:1.1.4, I've found a workaround keeping a reference to the onNeverAskAgain lambda from the Fragment that is constructing the permission request using constructPermissionsRequest; see sample code:

class MyFragment : Fragment() {
    private val locationPermissionNeverAskAgain : () -> Unit = { /* never ask again code here */ }
    private val locationPermissionRequest = constructPermissionsRequest(
        /* other settings here */
        onNeverAskAgain = locationPermissionNeverAskAgain
    ) { /* permission granted code here */ }
}

Probably library should declare onNeverAskAgain as a val on PermissionsRequesterImpl.