Viber unable to receive calls when phone locked

[Glavata]

On a Lumia 1020 with Black, on latest viber verson, 4.0.1.

When someone calls me on viber and my phone is locked/app closed I get no call notification. I then get a toast notification of a missed call. My friend on a 920 has no problem receiving calls. Any ideas what might be causing this issue?

Thanks!

 

[Glavata]

Reinstalled without linking facebook and now it works ok. Not sure if that had anything to do with it, or just a reinstall fixed it.