macOS says the app can’t be opened

macOS shows this for apps downloaded outside the App Store until they’re notarized by Apple. It’s a one-time step.

1. 1Try to open Paatu Cassette once, then close the message (Done).
2. 2Open System Settings › Privacy & Security and scroll to Security.
3. 3Click Open Anyway next to the message about Paatu Cassette and confirm with your password.

On macOS 14 Sonoma or earlier, you can instead Control-click the app in Applications, choose Open, then Open again.