FLStudio's plugin manager is not up to date with the latest versions of the SDK.
This was taken from the page "VST 3 Locations / Format" in the SDK documentation:
[quote]
On the Windows platform a VST 3 Plug ...
FLstudio 20 and im having issues downloading Vsts. I have tried to upload vets from multiple sites, Splice and VSTplanet. I understand how to go to plugin manager and scan to find the VST. However what im confused about ...
Essentially, I don't know how to change the plugins I bought from trial version to the full versions. I bought the Signature Bundle and a few of the plugins/VST changed from their trial versions to the actual full version ...