I see that this was reported and a fix was made for it. During the last months of 2018 there was a release-freeze at Linnworks. We are now starting to release the fixes that are queued up bit by bit. The fix for the report you mention is due to go out this week.
The built in report has been broken now for several months. I do have a ticket open for it, but I would have thought that considering this is a built in report offered by Linnworks you would be keen to get it fixed rather than people having to keep asking.