How are you attempting to rescan the server? Remember that doing a manual rescan from within Lansweeper does not invoke an agent scan; rather, it will attempt to scan via SSH credentials, which may not work if the appropriate credentials have not been configured. Even then, that method of scanning is subject to the Scanned Item Intervals, and I believe the default is that Linux users and groups are only scanned weekly:

Otherwise, as suggested by ErikT you are stuck waiting for the agent scan interval to pass before the agent will rescan the data, and you will need to confirm what the scan interval is for the lsagent group the asset belongs to; e.g.

Hope that helps point you in the right direction. By the way, Esben's Protip on Linux Least Privilege Scanning provides some pretty good details on how Linux scanning works, and the commands it uses to retrieve information.