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 ...
FL to the right .dll?
Oh I probably should mention that this project was created on the same machine I am trying to open it on right now. There haven't been any changes made to the file & folder ...