A knowledge base article on resolving this particular error can be found
here.
You may also be interested in scanning with LsPush instead. The LsPush.exe can be used on client machines to initiate a scan. It takes a full local inventory of the client machine by itself and does not rely on the Lansweeper service to perform the scan. This makes it ideal for scanning difficult to reach computers.
LsPush is part of version 4.2 of Lansweeper, which was just released. Our latest installer can be found
here.
More info on scanning with LsPush can be found
here.