I have Viber installed on my Galaxy Note, and most of times when others called me, my phone did not ring (in standby mode). Only after I turned on the locked screen, connected to the Internet, then only I saw missed calls from Viber. Was this caused by installation of juice saver app e.g. 2x battery? Did anyone experience this?

Ok but now I have all juice saver apps disabled. Anyhow just now after my phone has been in idle mode for more than half an hour, when I turned on my screen then I saw Viber icon was in transparent purple instead of purple. It only turned back to purple after I went into Viber (I didn't exit from Viber anyway). Does it mean Viber was disconnected?