Try to change platform target from "AnyCPU" to "x86" (see screenshot).
If you use AnyCPU, the machine will try to use 64 bit assemblies. But Esri assemblies are 32 bit. This is why the installer cannot find the referenced assemblies from your plugin. You have to constrain your .NET plugin to 32 bit by setting platform target to x86.
This issue has taken much time for me to resolve when installing my own plugin on a customers machine some months ago...
Best regards, Stefan