I had the same issue after I upgraded from Ventuz3 to Ventuz4.
The new Ventuz version has a new location and is seperate from the ventuz3 version.
Means you have to copy all .dll files from V3 to V4.
In my case was it in the following folders:
C:\Program Files\Ventuz Technology Group\Ventuz 3 (x64)
C:\Program Files\Ventuz Technology Group\Ventuz 4
It worked for me.
Best regards
Mr. Tompkins
