If possible, can you give some hint about a failure when trying to load PlugIn4 which uses dll (Plugin3).
The same procedure in RH 5 worked fine.
You can find both RHP (Plugin4) and used DLL(PlugIn3) at the following link:
[VS 2017 solution] (https://www.dropbox.com/s/09hc9r2galpzu4z/Test%20dll.rar?dl=0)
Thanks a lot for your support