Investor/RT is built using a development framework that is dependent on Apple’s “Carbon Framework”. With Catalina, Apple has discontinued Carbon, a legacy technology created years ago to bridge Mac applications to Mac OS X when it was first introduced. Without Carbon, our app cannot run on Catalina. Carbon is supported under Mojave and earlier and that is our only solution for native Mac Investor/RT. You can of course run Investor/RT on your Catalina system using VMWare and the Windows edition supports a wider array of market data and brokerage order routing system that our native Mac implementation could.