I am having the same problem. About a month ago the trusted places option stopped working at home. Very annoying to have to unlock it everytime to check messages or to text.
Be grateful you don't have an s7. The latest updates have stopped the edge night clock, smart lock no longer works and the phone keeps going blank and restarting itself. This is my 3rd s7 in 18 months. First one caught fire, the replacement never worked properly and now this one is only a month old so it isn't the age of my device. It's out of the box.
I did notice that there is some process that times out in app. 4 hours, like many others have been complaining in multiple other conversations around the web.
Smartlock operates fine, if you get in and out of your trusted place every 3-4 hours. If you stay there it will stop operating after that time and requires Restarting the phone, in order to simulate the situation that the phone has been away. I have not been able to find out which process it is that I could kill and restart, but this is quite annoying. Of course restarting the phone is quite easy: one has to insert pin code twice and then get another max. 4 hours of time that doesn't require continous pin code inserting. Still I hope that Google/Samsung would investigate and fix this issue for good.
The procedure that works 100% of time with my phone, when Smartlock stops working because the time limit.
1) Restart the Phone
2) Insert both pin codes to get to see the phone desktop
3) Open Google Maps to check that phone locates you correctly, leave Maps on
4) Close the lid or turn off the display and wait about one minute
5) Turn on the display, and it shoud open without requiring the pin, kill the Maps and enjoy max 4 hours without needing to insert the pin code. (Of course same thing can be achieved by going to Grocery store and back, perhaps this is the hidden agenda to get users to go out and keep fit X'D )
I had the problem the other way round - it wouldn't unlock in trusted places.
I solved it on my phone. I switched off every other SMART lock feature and just left Trusted Places on. Been working for over a day now after having not worked at all for 3 or 4 months.
Obviously one of the other Smart Lock features - voice, trusted devices or on-body detection is interfering with trusted places, but not sure which one at this stage.
Updated my samsung account location and now the location smartlock has worked for the 1st time ever.
They must have finally done something. My smartlock has not forgotten it's supposed to be unlocked in a while now. It's a major improvement.
My older Samsung J5 still doesn't understand the phone being in smart lock area after 4 hours. Earlier I had to resort to Restarting the phone every 4 hours to make the phone understand that it is still in safe area. Yesterday I did find a solution that doesn't require restarting the phone =):
1) Once the phone starts to ask for Pin again, log in with a pin code
2) Open the list of currently active applications and Close the Google Maps if is active by dragging it away from the screen.
3) Open the top menu and Turn off the Location needle icon.
4) Open the Google Maps and wait until it asks to use Location and Allow Maps to use it, wait until you see the little Pin icon on the top of the screen and see that phone has find your location correctly.
5) Leave the Google Maps active on the screen and close the lid or turn off your screen. When you open the lid or screen a bit later you should find it working for the next 4 hours!