Views:

As the offline editor for Pro Series is a 32 bit app it will only run with Mac OS which supports 32 bit applications. 
The last Mac OS to support 32 bit apps is Mojave. 

While Sierra, Hi Sierra and Mojave are 64 bit operating systems they allow 32 bit emulation, meaning the app will run (after showing a warning message).

Please note that this requires a WiFi connection for operation.
The device providing the WiFi connection (mobile phone Personal Hotspot, train WiFi, router etc) does not require an internet connection. This allows the editor to continue to function as normal (although the SAVE and LOAD functions do require a WiFi connection, but not internet access).

Catalina OS however does not allow 32 bit emulation and therefore cannot run the offline editor app.