There is a thread here complaining that it's not possible to download Apps to the Kazam 348 and I have the same issue.
Having 'googled', it would seem that others have the problem too and neither Kazam or Google Play Store support have resolved it. There is, though, a curious anomaly in the behaviour that might point to the real issue being with Virgin: that is people have been able to download when connected to a third party wifi, rather than Virgin mobile or Virgin broadband.
Is there a possibility that some aspect of the Virgin protocol conflicts with the handshake between Kazam and Google Play Store?
Whatever is the answer to this question, I need a solution to the issue, or Virgin will be getting the otherwise useless phone back.
For me it has now been some 7 weeks since I was last able to update/download Play Store apps on my phone while at home (or over mobile data for that matter). I realise that the underlying issue is probably something Kazam need to sort out ..... However, the problem only shows up in some circumstances and this does make me wonder what suddenly changed at the beginning of April.
My home internet connection is 200 MBit/s via a Superhub 2ac. The internet connection at work (in the same village) is a 100MBit/s VM Business connection with Dynamic IP and a Hitron router. I experience no problem using Play Store at work or when accessing the internet through a friend's BT connection.
I reckon that I have played with every possible setting on my home router - but all to no avail. I would be very interested in anything you manage to find out.
I haven't got any further either, other than the advice from Kazam to use Aptoide to download and update apps. That does actually work, although I wouldn't say it's a perfect solution by any means and I have had one glitch where I couldn't update the 'Google Maps' app.
It does seem ludicrous that people are waiting so long for a fix.