Halion 6.4 Crashing on startup

Just been checking through all my Cubase software and hardware drivers to ensure all on latest versions.

Loaded Halion v 6.4 and it crashes immediately after opening its main window. Downloaded again and reinstalled but same effect so overwriting its install files with new didn’t work. Im using it on Mac Mojave. Problem may have started after install on my new AX4R-T as it was working OK previously.

I saw there were several posts a while ago about others getting this problem but can’t find any posted solutions.

Any ideas anyone?