The reason you are seeing a black screen when trying to log into Arcade is because your browser is below Safari 15. To fix this issue you will need to update your browser to the latest version available.

For example, if you are using Safari 13 on Catalina, please update to Safari 15. You can do this by navigating to System Preferences > Software Update > More info... > select Safari from the list > Install Now. If you do not see Safari listed, please update to the latest build of your OS version. You should see it in the More Info list as well.
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If you cannot update your OS to Catalina, we encourage you to install a previous version (2.8) of Arcade that might work better with your system. You can find that here: Arcade Compatibility Chart & Legacy Installers