Make sure the issue really lies with your macOS version. To do so, try to install the software manually. If it is incompatible with your macOS version, it will tell you. In that case, there is nothing we can do to help you install the software, but we can add a depends_on macos: stanza to prevent the cask from trying to install on incompatible macOS versions.
Help us by submitting a fix. If you get stumped, open an issue explaining your steps so far and where you’re having trouble.