To allow the EndNote download from UniSC Software Centre on your Mac, you will need to adjust your Security & Privacy settings to allow apps downloaded from "Anywhere" or "App Store and identified developers".
The process in a nutshell:
1. Open System Settings
2. Navigate to Privacy & Security:
3. Access Security Settings:
4. Adjust Download Permissions:
The EndNote installer on UniSC Software Centre is controlled by UniSC IT. It was checked by IT for suitability and threats. This may explain why it is not considered to by an identified developer.
Be aware, when you first download EndNote 21 onto a Mac, the Cite While You Write option may not work. Go into Microsoft Word > EndNote tab > Preferences > Application > EndNote. This changes the connection between Word and EndNote from online to desktop.