Make sure the activity settings for your chosen activity (Run/Walk) specifies 'Use Map' rather than 'Follow Course'. Only 'Use Map' will route you using the watch routing feature - and display turn by turn navigation including distance to next turn.
you do need a routable map for this to work.
No, you don't.
Not sure if this is the same problem, but II just verified today, that there are no turn by turn directions on my Fenix 6s, when using a round trip route created on the watch, There is only the tiny map which makes it almost useless when running in dark conditions. I think Garmin should fix that in a firmware update as soon as possible, as this is really a big let down on such an expensive watch.
Just uploaded a gpx file to my Fenix 6s, and there is no turn by turn direction at all. The exact same gpx file worked fine on my Forerunner 735 XT with turn by turn directions.
Found this from "HarryOnline" - and it works fine.
In the activity settings (e.g. Run Settings), there is an option Routing - Courses. Selecting 'Follow Course' is the default option, but you can change it to 'Use Map', then you will get turn by turn navigation. If the course is from a track, you will see a lot of blue dots for all the waypoints, which is disturbing. If the course is from a route, it will have fewer waypoints, but there is a risk that the route will be changed if it was generated using a different map.
I tried that last night, but my Garmin kept trying to force me to take the shortest road route back to the start/finish rather than directing me along my course. Any idea what I did wrong?