How to fix: Duo stopped locking when closed

I have the same problem. At first, it would happen from time to time and I thought it was because I closed to device too slowly, softly.

Then, after closing it with more confidence it didn't happen. Today it just won't lock when closed.

I have also looked at your phone app to see if it would prevent it from locking the phone but not. 

Thank you!

My Surface Duo has stopped locking when I close the device. I have explored all of the settings I can think of that might cause this, including Smart Lock, which is turned off. Does anyone know how to turn this back on so my device will lock when I close it without having to press the power button? Thank you. 

Found a fix. It was linked to your phone app. You can find a thread with solutions on reddit. 

https://www.reddit.com/r/surfaceduo/comments/iqk8r3/not\_locking\_on\_close/

I followed the step by step shared in the thread. 

I hope this helps!

Not sure if this helps anyone but my Duo did the same thing. I changed the wallpaper and it immediately started working again.

My case it was google play services. Force Stopping it fixed it for me.