So you probably came across these highly informative messages at some point:
What Revit is usually trying to say is that there isn’t enough disk space and it cannot sync with central. The above were displayed on the same project, whose units were set to Imperial, so I’m not sure why Revit had a metric fit there for a moment. It appears that disk space is perhaps being measured per length of track on the disk? Ah shucks, don’t try making sense of it, just know to look at how much hard drive space (or perhaps network disk space) you have next time your users get these gems!