Hi,
you’ve installed already PRO version 4?
Remind me, please? You are running windows? Close Cubase and please delete your preferences folder and re-start Cubase.
C:\Users\YOURUSERNAME\AppData\Roaming\Steinberg\Cubase 9_64
Please also check if PRO Version is installed correctly. After you have re-start the app, check your Plug-In Manager (Menu / Device / Plug-In Manager). Check that “VST Connect PRO” ist installed. Check that PRO is written upper-case. It is version 4.0.1.7?
See you,
Michael.