Having the same issue. Just purchased the Ultra plugin promotion you had. all the new Ultra Plugs aren’t showing up in s1 4Pro. I’m a windows platform.
I had the same issue with the H3000 too. The .dll files have to be placed into the VST3 folder because that’s how S1 uses VST3 plugs.
on Windows if it’s an x64 VST3 it has to be in Program FilesCommon FilesVST3 to scan and load.