If you have a VST3 with a long name that won’t load, longer than 31 characters in length, such as “Izotope Ozone 7 Vintage Compressor”, which is 34 characters in length, here’s what you need to do:
1) Install Mixcraft 8 Build 408 (or newer)
2) Select File->Preferences, click on the Plug-Ins page, and select “Re-Scan All VST Plug-Ins”
The scan will take a while, unfortunately, but this is necessary to update the VST3 information in the registry. The problem is fixed in builds newer than 408.
As an alternative to the method outlined above, you can edit your Windows registry by going to HKEY_CURRENT_USER\Software\Acoustica\VST3 and deleting the information for the VST3 plug-in with the long name. Next time Mixcraft 8 Build 408 or newer is run, it will re-discover the VST3 and store its information properly.