How to add C++ plugins to SketchUp editor

Dear friends,
all above looks like the SO files should be functional. What my problem is:
I have programmed several Ruby C++ extensions compiled as DLL/SO files in Windows.
I started in 2014 with 23bit and tried some more with 64bit since February 2017.
All went well peacefully with Sketchup 2014 32bit and 2015 and 2016 64bit.
This might make me blind somewhat because now I have been stopped dead:
With Sketchup 2017 my Ruby code refuses to load SO files.

A code like this:

Sketchup.require ‘C:/Users/<…>/AppData/Roaming/SketchUp/SketchUp 2017/SketchUp/Plugins/3E_SO_Test_UI/SO_Test_DllMfc.SO’ #I tried DLL and to remove the file extension as well…

results with

File load error (C:/Users/<…>/AppData/Roaming/SketchUp/SketchUp 2017/SketchUp/Plugins/3E_SO_Test_UI/SO_Test_DllMfc.SO): Could not find included file ‘C:/Users/<…>/AppData/Roaming/SketchUp/SketchUp 2017/SketchUp/Plugins/3E_SO_Test_UI/SO_Test_DllMfc.dll’
false

There is no rescue exception so no more clue what is wrong.
Nevertheless it looks like the file content does this. When I just replace the file with just “…/something_empty.rb” without touching one more letter in the path, the file is loaded OK.

Further notes:
All my projects are based on the

download.

My environment is VisualStudio2010.

This test I perforned with the “Hello world”.
I compiled it in x64 platform with libraries titled “2.0” and “2.2”. I double checked this in the project configuration.
When I used “2.2” then the SO file ceased to work in Sketchup <2017 but there was still a relevant error message like “improper version of something”.
In Sketchup 2017 both “2.0” and “2.2” compilations results in the same “Could not find included file”.

Please where to look next, I am short of ideas?