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 64bit signature, and i recently bought Output's movement, and i downloaded the 64 bit one as well, the problem is that it kept crashing in fl and i looked up on the forums and i found ...