Sdlplugin installer - Studio versions grayed out

I have developed a plugin for Studio 2017. The sdlplugin file is signed by SDL and when I install it on my computer, I can select Studio 2015 and 2017. 

A user tried to install it on his machine, but now the Studio versions (exactly the same builds that I have on my machine) are grayed out. Another user had no problems at all and could install it without any problem.

Does someone have a clue what may be the root cause of this? Is there are log somewhere that shows the root cause?

Thank you,
Henk