My wife has a Lumia 640XL with the smartthings app, and I verified that ‘geofencing’ is allowed and turned on for the smartthings app, and it worked yesterday but today, nothing. she is at Costco and it still says she is present and she just called me from her phone so I know she’s got it with her 
Any tips on this? I am trying to get an automation routine going for when she gets home (opening the garage door for example) but if it never knows she left it isn’t going to work.
Thanks!
Make sure it’s allowed to run in the background. I doubt that’s the problem thought. Presence detect has been awful on all three platforms. There are dozens of posts just like yours on here. Some people use two devices or apps in the hopes that one of them will work. My house has a mix of Windows and Apple phones and neither work reliably. I’ve given up on that feature.
Here’s my story. I carry my iPhone in my pocket. I’ve learned that when I have it in my pocket when I depart/arrive in my car, location services is flaky and my presence is not reported properly with ST a majority of the time (coming or going). But when I remove it from my pocket and place it on the dashboard or in the cup holder when I am driving, my presence is reported properly most of the time.