Hi Quinn, Thank you so much for your reply! I created the demo app as you suggested and I did notice an issue. In my failing main app, I didn't enable Hardened Runtime. By enabling the Hardened Runtime, the main app simply crashes after launch for some reason. I am wondering if it is mandatory to have Hardened Runtime in order to access the Photos library in a Sandboxed app? In Xcode, the UI seems already tell me that it is required, but I am wondering if you could confirm it.

I actually built the app into multiple folders / versions for testing purposes. I think my pain point is that App Store forces me to delete all my local builds, to install the app to the 'Applications' folder properly. I am wondering if you know a way to clean up the app cache or registry (not sure what is the name though), so that macOS doesn't know that it has the app installed, this way I could run such a command prior to installing app from Mac App Store. Thank you!