Mac has the security settings to allow apps from the App Store and identified developers. When you downloaded an app from the internet or an unknown source other than App Store your Mac may warn you. The first time you launch a third-party app from an identified developer, your Mac asks if you’re sure you want to open it.
Sometimes Apple may tell you the app is damaged and can’t be opened, you should eject the disk image
This message doesn’t necessarily mean that something is wrong with the app. Sometimes the error message may be incorrect. You can try to allow applications downloaded from anywhere from the system security setting see if you can get rid of the error message.
Access Mac System Preferences, click Security & Privacy > General. Click the lock icon at the bottom-left and enter your password to make changes. Select Anywhere under the header “Allow apps downloaded from.” Enter your password again when prompted. Try to install the app again see if any help.
Can’t find Anywhere under Allow apps downloaded from?
The “Allow applications downloaded from anywhere” option is hidden by default in Gatekeeper since Mac Sierra. Mac does not users to allow all apps to keep their computer safe. Advanced Mac users can reinstate the Anywhere option in Gatekeeper from Terminal.
Open Launchpad on Mac. Select and launch Terminal. Then type in the following command:
sudo spctl --master-disable
Press Enter or Return on your keyboard. You will be prompted to enter your Mac password. Type in your password and press the Enter or Return on your keyboard again.
Go to System Preferences > Security & Privacy > General again, this time you should see the Anywhere option in the Allow apps downloaded from section. You can enable it to allow all apps or allow third-party apps downloaded from anywhere from there.
You can also reverse this and go back to the default strict Gatekeeper settings. Also in the Terminal windows, enter and execute the following command string:
sudo spctl --master-enable