Some plugins, like D-50 from Roland Cloud do not display any parameters in AU or VST3 versions. This works with earlier versions of JUCE.
Unfortunately I cannot tell exactly which version worked, but fairly certain that JUCE 5.2 worked ok.
Here are the two screenshots of audio plugin host diplaying the parameters for D-50. The dark image is the newest 5.4.1 JUCE and the white one is an earlier version which obviously works.