If you try to open an app that isn’t registered with Apple by an identified developer, you get a warning dialogue. This doesn’t necessarily mean that something’s wrong with the app. For example, some apps were written before developer ID registration began. However, the app has not been reviewed, and macOS can’t check whether the app has been modified or broken since it was released.
To override your security settings and open the app anyway go to the Apple official Support article Safely open apps on your Mac and follow the steps as per your issue:
Source:- Apple Support