Apple has introduced many security features in macOS 10.15 Catalina. One of them is requiring 3rd party developers to include a certificate in their apps in order to validate that the software is free of malware or viruses.
If you are using Screens Connect 2.x or 3.x on macOS 10.15, you may encounter this warning:
Since these older versions of Screens Connect are very old, they no longer meet the new requirements. The permanent solution is to install Screens Connect 4.x, which does meet all requirements and also has more features.
In fact, we highly recommend to install Screens Connect 4.x on all Macs running macOS 10.11 or later. Older versions of the software are no longer maintained and are only made available for older macOS/ OS X versions.
To update to the latest version, simply go to the Screens Connect product page and scroll down to the bottom of the page to find the appropriate link.