I have setup a server to test the functionality before rolling it out company wide. We have a dedicated server, directly connected to the internet. It passes all the firewall tests, and seems to be operating correctly. For initial testing I have a Windows laptop with the 3cx client installed, and working. Then on a Samsung S6 Edge, I have the latest Android app installed. If I have the program open and visible on both devices I can call back and forth without issue. However, if the Samsung is with the screen blanked, i.e. cover closed. around 50% of the time, the Push seems to work and my phone rings. The rest of the time, there is no visible or otherwise indication a call is incoming, but it must be at least part working, as when I open the phone next, it shows a missed call. I have today download all the latest version, server, Windows client and Android Client, so they are all the latest versions. As it stands I have little confidence I will not miss an important call as the phone doesn't ring. In our line of work, we cannot afford to miss calls. The fact it works perfectly for around 50% of the calls leads me to believe I have completed the installation correctly. Does anyone else have any experience of this? And if so, what is the fix? Thanks in advance.