I am not sure if this has been reported here as I couldn't find it ...
If you have updated to the V4.1.18 GO4 and had not downloaded maps then you can still do this ... while not plugged into the RC just keep starting GO4 and click on the three bars in the top right of the screen. Repeat this until the option appears.
So as follows START GO4 CHECK DROP DOWN MENU ( not there ) close GO4 and restart and repeat until offline maps appers in the drop down and then download your required offline map.
If you have updated to the V4.1.18 GO4 and had not downloaded maps then you can still do this ... while not plugged into the RC just keep starting GO4 and click on the three bars in the top right of the screen. Repeat this until the option appears.
So as follows START GO4 CHECK DROP DOWN MENU ( not there ) close GO4 and restart and repeat until offline maps appers in the drop down and then download your required offline map.