Hello Olivier,
Thank you for your message.
It seems like you need to set up the
Address book sync feature on your RU Server - this feature will allow you to have an automatically synched address book on both RU Server and Viewer. You can follow
this guide to enable and set up the address book sync feature.
In case if the address book feature was already set up earlier, you can add the synchronized address book to your Viewer by following
this guide (make sure to select
Remote (synchronized) kind when importing a cloud book.
Hope that helps.