On your phone uninstall the galaxy wearable app and then reinstall from play store, i had to do it twice but my watch is now fine, hopefully it will work for you.
I did send my watch 46mm back to repair this AOD problem.
In one week the new Watch arrived, (TOP SERVICE COOLBLUE BE) but this new Watch have the same AOD problem.
I discovered the main solution after seaching for ours.
Just set in health app the hartbeat on " NEVER"
Now the AOD is working perfect.
To measure the hartbeat I push manualy.
Hope this is helpfull for all.
I will inform Samsung about this, they will resolve this problem hopely soon with an update.
Just remove the night mode, it will work. Most likely, the night mode is on. Toconfirm, check if there is a moon sign on the 12 point. If yes, then go and disable it.
The issue is that when you reset it, the night mode is disabled but you go back an enable it, then the problem comes back.
I did what you wrote, but this did not work for me.
When I restart the Watch the problem is solved for a couple of days.
After some days the AOD turns black again.
When Samsung do not solve it with an update I will return the Watch again.
All recommended help on this forum unfortunately does not work.
I received my galaxy watch through EE a month ago.
The AOD didn’t always work, any exercise I started cut off after 20 minutes and I got the ‘clean sensor and place of wrist’ message when trying to manually measure HR.
I found that the 3 problems are linked. When the AOD DOES work, so does the exercise and HR sensor.
I thought it was a broken device so returned it. The 2nd watch does exactly the same as does my THIRD watch that arrived yesterday. I went into my local EE store and they confirmed that all the settings were correct.
This is really annoying me
I have the same problem, today I send my watch back for the second time.
I bought the Watch because I love the design and the top battery.
So with that battery you can use AOD for more than 2 days.
But when the AOD fails the Watch is useless for me.
Now I wait for the reply of my shop where I bought it.