Lost-phone apps do not work for my S5 I am struggling to understand what's going on here! When I first got my phone, I signed up for Samsung's service for finding a lost phone. But, not too long after it simply stopped working. I finally decided it's time to try something else. So, I tried Lookout as well as the Android Device Manager. I offer this information only for history.

Now, I have pretty much given up on everything except Android Device Manager. It is currently set as an admin to my device. But, it only works if the screen is on! If my screen is off Google cannot find nor ring my device. If my screen is on (even locked) it has no trouble. What can I do?
Perhaps, you have set the parameter in the settings, that all network connections are disabled when the screen is off. 

Or aybe you should try another anti theft guard, such as the avg antitheft app.