System will create a new instance of PKIssuerProvisioningExtensionHandler for every method call. This means you can not share data between method calls via private class properties!!! But you may use another approach, like global variables outside of the class.

Make sure your extension's iOS Minimum Deployment version is lower than your physical devices' iOS version, otherwise the extension is being ignored by the system. Happened to me.

When you create Extension targets in XCode, it will usually assing the "Minimum Deployment" target to the highest iOS version. In my case it was iOS 18, while my physical device was 17.5.1. Lowering this target made my app visible in Wallet.

I also confirm that it works correctly now in iOS 18.2 Beta 4.