Hello, thank you! Create brush only works when there's an active selection. For more information about brushes, you can read our documentation: https://orama-interactive.github.io/Pixelorama-Docs/concepts/brush
Unfortunately, I don't own a Mac so I can't properly test the macOS version and we rely on the community's help and feedback. Pixelorama's macOS binaries are being generated through GitHub Actions workflows, which run on macOS and generate a .dmg file, which should have executable permissions, but it's unsigned and not notarized. So, in theory, disabling Gatekeeper should work. I'm not sure why it doesn't, but we'll do what we can to find a solution.