This is a macOS security issue. We suggest you use the following instructions:
After downloading the installer, move it to the "Applications" directory. Then:
This application is saved as an exception to your security settings, and from then on, you can open it with a double-click - just like any registered application.
Note: Another way to create an exception for a blocked app is to click the Open Anyway button, located in the General pane of the Protection and Privacy preferences. This button is available for about an hour after you try to open the app in question.
To change these preferences on a Mac, choose Apple menu command > System Preferences, click on Protection and Privacy , and then click on General.