In cases where your map displays a straight line between points on your trip, the first thing to check is whether you are connected to the internet - no internet connection may prevent road routes from being displayed.
If your internet is connected but the map still shows a straight line, you can add a 'Waypoint' to help redirect it, see Can I make a Trip Planner choose a different road than the one selected.
WikiCamps. By campers, for campers.
Article relates to Android, Apple, and Windows devices.