Hi, I created an empty new audio plugin project in Juce 5.4.3.
VST-3 builds in Visual Studio 2017/Win32 are not recognised in both Cubase 5.1 win 7 64 and Reaper win 10 64 that I ve tried although they run ok in the juce plugin host.
Builds from Juce 5.3.2 are recognised fine.
A quick internet search tells me, that Cubase 5.1 is from 2009 and likely to be pre-VST3…
Are you building with legacy VST SDK?
You are probably aware, that VST had to be removed, and if you have the License, that you will have to set the path to the old SDK manually…
Reaper’s bit bridging (that allows for example to run 32 bit plugins with 64 bit Reaper) does not work with VST3 plugins. If you want to test a 32 bit build of your VST3 plugin in Reaper, use the 32 bit version of Reaper.