How to fix: Duo stopped locking when closed

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

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

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!

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!