On the 23rd December, Apple announced an update to the Notarization prerequisites for non Mac App Store apps, adding a new deadline of the 3rd February for apps installed outside of the App Store (https://developer.apple.com/news/?id=12232019a):
“In June, we announced that all Mac software distributed outside the Mac App Store must be notarized by Apple in order to run by default on macOS Catalina. In September, we temporarily adjusted the notarization prerequisites to make this transition easier and to protect users on macOS Catalina who continue to use older versions of software.”
Followed by:
“Starting February 3, 2020, all submitted software must meet the original notarization prerequisites.”
They also added:
“If you haven’t yet done so, upload your software to the notary service and review the developer log for warnings. These warnings will become errors starting February 3 and must be fixed in order to have your software notarized.”
If you are unsure whether your apps are notarized, you can use the following Terminal command:
codesign --test-requirement="=notarized" --verify --verbose /Applications/MyApp.app