GUYS we cannot use one dongle to connect two monitors; since the upgrade, I suppose. I just used two different dongles because my Macbook only has the usb-c connectors. It worked! Both monitors were detected. Here is where I found the solution: https://setapp.com/how-to/troubleshoot-multiple-monitors "Don’t chain connections together. Some monitors with older connections require adapters for use with Macs, sometimes more than one. Chaining adapters together can cause your monitor to not be recognized."