Maps

What kind of paths are you trying to route on?  In my experience with TopoActive 2017 NA, the Garmin maps are inferior to the free OSMs (http://garmin.openstreetmap.nl/) in both the city and in the backcountry, so I've disabled them entirely.  For city routing I use the Generic Routable maps, and for hiking and cycling I use the Routable Bicycle maps.  The TopActive maps are ok for cycling in the city but they lack useful POI data and don't work for automobile routing.  As for the Routable Bicycle maps, I've found them to be superior to TopoActive both for cycling and hiking as they seem to have far more useful trail and point of interest data such as backcountry campsites.  

Where were you when you were calculating round trip courses before? Which map? 

If you are certain you were using the same map before then perhaps reload them from Garmin Express.

Thanks I've tried several places where I live and the same message comes up even though it worked in those places with the pre-installed base map before I loaded the Topo active ones.  If I reload them presumably they won't be loaded twice and take twice the space?  On a related issue do you know how I can tell how much memory on my garmin I'm using up with the maps?

I used the tutorial from https://www.dcrainmaker.com/2019/08/how-to-installing-free-maps-on-your-garmin-fenix-5-plus-forerunner-945-or-marq-series-watch.html

It stated that you have to use routable maps, maybe you have to get a different map version?