Having a problem seeing my VST’s. I add the dll’s to the VST plugin folder but they don’t show up in the insert any more. I’ve added dll’s many times before and never had any issues but all of a sudden they’re not showing up. It started out that some wouldn’t show up after adding them but now none are.
If you are still having problems…
Have you made sure that CB8 is looking to the same (or correct) folder? Check it as follows:
Go to Devices > Plug-in Manager. You can then click on each plug-in on the “VST Effects” and “VST Instrument” pages to see it’s path in the bottom half of the screen called “Plug-in Information” (the italic “I” icon at the bottom must be pressed to see the paths). You can also see a list of the VST2 plug-in paths by changing the settings for the “Plug-in Information” section by clicking on the “gear” icon at the bottom.
Regards 
Having the same issue.
Cubase 8 can’t seem to find some of the DLLs in the Program files\vstplugins directory
It can’t find Alchemy instrument
It can find IK Multimedia’s Arc2
but fails to find any of Ik Multimedia’s T-racks DLLs.
along with a bunch of other ones.
Surely this path is the default path for 3rd party plugins?
Cubase 7.5 had no issue with this.
Moved Alchemy into its own directory and now it can find it.
Tried the same with the dozen T-racks pluginsm and Cubase still can’t find them.
Update: Removed the directory out of the list. Re-added it and then re-scanned. 44 new effects found.