The SAGE Converter (a 32-bit standalone application used to bring your own audio to Stylus RMX) will not work in macOS Catalina. The latest version of Stylus RMX includes an Import REX Files feature in the Stylus RMX standalone application that can be used to bring your own audio in Stylus RMX.
Update to the latest Stylus RMX software version and the data updater here to use the Import REX Files feature.
Click here for information on how to use the Import Rex Files feature.
After you have installed the latest software update, open RMX as a standalone application, click on the View drop down menu at the top left corner of RMX’s window or your computer screen to see Import REX Files – then this means you are up to date with 1.9.8g.
The update that was installed isn’t a major change to Stylus RMX (it’s purpose is to install the new Import REX Files function into the standalone of Stylus RMX). Therefore the software version in Stylus RMX will remain as 1.9.8c. As long as you see the Import REX Files option as shown above, you are up to date.