On macOS, users aren’t restricted to the Mac App store and its library of apps. Plenty of great apps are distributed from outside the Mac App store and installing them is a simple process. Apps that are from the Mac App store are subject to review and scanned for malicious content. Apps from outside the Mac App store have not been scanned so when you install them, macOS runs a scan on it. When macOS tells you to contact the developer to run the app though, it’s a road block. Here’s how you can fix the ‘Cannot check for malicious software’.
Read the full error message
You’re going to see an error almost always when you try to run an app downloaded from the internet i.e., outside the Mac App store. As such, it’s important to read the whole message to understand why the app is being blocked. If the message tells you to contact the developer in order to be able to run the app, you may not be able to run the app. The message may be a simple signing issue or macOS not being able to scan the app, or it may be because it’s a 32-bit app.
If it’s a 32-bit app and you’re running Catalina, there really isn’t anything you can do. You have to wait for an update. If that’s not the case, you might just be able to run it with admin rights.
Fix ‘Cannot check for malicious software’
Run the app and once you see the error message, dismiss it. Open the System Preferences app and go to the Security & Privacy preference. On the General tab, you will see an option to open the app. Click the pad lock icon and enter your admin password. Click the Open Anyway button and you’ll get another error message telling you the app needs to be updated.
This error prompt will also have an Open button which you have to click. This will open the app.
Assume all risks
Any app that you have to force run like this comes with some risk and when you choose to run an app like this, you assume all of it. It helps if an app is open-source since anyone looking to package malicious content is unlikely to put the code out there. That said, apps that aren’t open source may also be blocked and as such, they pose more risk. Make sure you trust the app and the developer before you run it.