Announcement from EndNote
Apple will be releasing macOS 10.15 Catalina this fall, which will impact the desktop version EndNote.
EndNote X9 for macOS will be extensively updated for compatibility prior to the launch of Catalina. If you already have EndNote X9, please install all updates as they become available to avoid interruption in your workflow.
If you are running EndNote X8 or earlier, EndNote recommends updating to EndNote X9 as based on early information from Apple, as X8 will not work with macOS Catalina. Alternately, you may keep working on your current macOS version.
For more details, please visit https://support.clarivate.com/Endnote/s/article/EndNote-for-Mac-macOS-Catalina-Compatibility