Watch not showing tracks for navigation - how to fix or reset watch?

Go to Garmin\Courses folder and remove all files you want (do a backup before).

To have turn-by-turn indication on your courses, you need to activate the option.

https://connect.garmin.com/

Go To Training & Planning

--> Courses

Select or create/import a courses

--> Search for the radio button on the courses descriptive and activate it, then Send to Device.

To follow "Track" - Select your activity, then middle left button, then Courses, then select your courses, then Do Course.

I have never heard of such an issue. Are you sure your track is okay? How did you transfer the track to the watch?

I have removed all files from garmin\courses. That seems to have fixed that issue. One of the files in there must have gotten corrupted somehow. Now I can see the line to follow.

Is there a way to change the color of the course line? It appears as a dark gray line which looks very similar to paths.

Yes, a map theme can change the color. What map theme is active 'activity settings' (for instance Run Settings)-> Map-> Map Theme?

It was set to none. I changed it to Popularity and now that line is red. Thanks!

Just had this same issue and doing the same thing, remvoing all saved courses, resolved the problem. 

Thank you for posting your solution....a year later and still very useful.