Turbo.264 HD is no longer developed - it has reached the end of its life.  

It is a 32-bit app, so it will not work with any version of macOS that is 64-bit only.

The latest macOS release - 10.15 Catalina - is 64-bit only.  Turbo.264 HD will not work with it and future versions of macOS.

See this article for more information:

32-bit app compatibility with macOS High Sierra 10.13.4