Problem with running Multi in Omnisphere.
I noticed another phenomenon. After starting Cubase, Unify, I opened the Omnisphere in Unify, chose the sound and when I switched to Multi in the Omnisphere, everything crashed. I had to restart the system. But when I opened Unify in Standalone, Omnisphere and chose Multi, everything worked.
I dealt differently with the problem of opening MULTI in the Omnisphere selected in Unify in Daw Cubase. I started Standalone Unify, opened Omnisphere, turned on MULTI and saved the sound in my library. After starting Cubase, Unify selected the saved Multi sound and everything works. You can you can.
What do you mean by everything crashed? Did everything close down and disappear? Only Omnisphere? Or were you frozen and unable to access Omnisphere?
There is a problem when switching Omnisphere Multis in Unify. Omnisphere pops up a dialog warning you it is changing the Multi. This is normal behavior but for some reason, the dialog does not show up in the foreground (on top of all windows). Since you can't see the dialog it appears frozen. The solution is to hit the enter key on the keyboard and it will click the OK button and allow you to continue.
I don't know if that is the same issue you are having but is something to try.
Ableton Live 10, Omnisphere, Native Instruments, Diva, SynthMaster, Alchemy 1.55, Addictive Keys, Unify
I did as you wrote, I pressed the Enter key, Multi has loaded and everything works. Thank you very much for solving the problem.