Android does not range beacons when locked / screen off

Tried very hard to make it work, tried from the simplest code to using foreground service, when the screen is on, it works like a charm, if you turn it off I can see in logcat the messages that it started to range but no beacons are found.

This is a Xamarin.Forms app using the Estimote xamarin package v1.0.3. I could not find any documentation, source code, article, even in Android Native that could point me to the right direction.

Any help appreciated.