Activate turn by turn audio alert.

Perhaps:
Focus Modes>Activity>

I also have this problem. Created  a course today and enabled turn notification prompts but nothing showed up the whole run. Did another course and checked  all settings in focus modes, run, maps, navigation. Cant make it work 

.. Garmin-Laurie is this a bug?

Focus > Activities > Voice Commands > Audio Output > And choose the source where the workout prompts come from. You can choose Watch, connected device (phone or headphones).

But you should pay attention to what you connect the headphones to. If to a watch, the source must be the watch. If a phone, the source must be the connected device.

Dors not function for me , set to watch, turban notification set to on in the course , never got any turn indication, painfull discovery for a long hike !

Look at the priority of the Activity Focus Mode. Because it decides globally about the settings, and you change them in the power profiles. Unfortunately, I have detected 2 problems with this mode. In the case of stopping the training and giving the option "Resume later", AOD turns on even if it is turned off globally for everyday use. And the second issue, giving the option Turn on the screen in Focus mode for the display, and turning it off in the dedicated power profile, nothing changes. It still remains on, only after the set seconds (e.g. 8 or 15), it dims. Obvious bugs. I struggled for a good few months in Epix Gen 2 with damaged profiles and they do not work in Fenix 8 again...

I would also like to know. There is no available setting that I can see

No fix for me either

Sadly, it doesn't work. My headphones are connected to watch (I don't have phone when I run). I can see every turn by turn indication on the watch screen with the distance remaining before the next turn, but no audio alert on the watch or in the headphones. There is also no vibration on the wrist.

If it helps, I'm having the same problems with my new Enduro 3. I'm a long standing Garmin user as I've owned a Fenix 6X and a Fenix 7X Solar over the last 3-4 years. Hopefully that means it shouldn't be a noob error or RTFM issue for me!!

If I'm using navigation for a course and I'm on any screen other than the map I get no notification of a turn, either visually or from a tone. The red guidance arrow rotates 180° once I pass the turn and 20+ meters later I get the off-course warning which beeps and vibrates so those definitely work.

If I'm on the map screen I can see a turn arrow and the distance until I reach the turn comes up, but I get no vibration or beep. This had caused me to miss turns unless I constantly keep the watch on the map screen AND watch the screen, This didn't happen with my Fenix 7X Solar

I've tried my routes which previously sent turn notifications from the watch screen on my Fenix 7X.  I've also setup new routes using Komoot and Garmin Connect (making sure turn by turn notifications are set to on whole doing so) I still get nothing on the Enduro 3.....I even tried to set a round trip route from the watch.... I get no sound or vibration on the Enduro at any turn,  just the visual arrow and distance to turn (but again, only when viewing the map screen, on any other screen in the activity I get no notification at all.

This must be a bug! Please fix it Garmin as I love this watch otherwise  

Done the same. I believe a bug or a miss. Needs an urgent firmware fix