Having the same issue in 10.5. Everything was working fine until……..😄
cubase 10.5 was bogging down and I had too many directories trying to operate, pops, freezing etc.
so, I went to Cubase for help and they suggested typing “xcubase on all the files, and Cubase would reset a new directory. Lost all my songs (somewhere) and vsts. Finally got back my NI vsts but SD3 won’t point to Cubase. The stand alone works fine. Opens and plays. I get the path off the stand alone and type it in the Cubase VST manager, path not found. It’s not there.
I will take pics tomorrow to show what I’m doing.