The most likely case is what Fuchs said, make sure you are using the installer version of 4.3
There is a known issue where plugins dont work unless your project is C++ based, at least for packaged games.
If you want to use my plugin in a packaged game you will need to make it C++ based and install Visual Studio
This is something Epic needs to fix!
You can add your voice to have Epic resolves this here:
@Phystrontium
Congrats on your first post!
:)
Rama