Hi Jean,
It seems that the import plugin has not been installed correctly.
Please ask the user to check the "Programs and Features" list.
Does that have listed "Trimble Solutions ImportSDK, SketchUp Plugin 1.43 (x64 build)". I assume the user has x64 installation.
If this plugin is found, please uninstall it and uninstall Trimble Connect Desktop also.
Then user should download the installer again from connect.trimble.com and install it.
The installer should list all the plugins it will install, ask user to verify that the SketchUp plugin is listed.
Then it should be checked that the plugin is now visible in the "Programs and Features" list.
If the SketchUp plugin is not listed in the list, even after reinstallation, in this case user needs to use Microsoft's tool to fix the removal/installation of the SketchUp plugin. Here is the link for this tool:
https://support.microsoft.com/en-us/help/17588/fix-problems-that-block-programs-from-being-installed-or-removed
If this tool is used to remove the plugin, then user would need to install Trimble Connect Desktop again to get the missing plugin.
Hopefully this helps.
Best regards,
Marko Myllymaa