SafeSky dropout despite internet connection

I was flying at about 2,000 ft in the UK recently over a fairly populated area with SafeSky on iPad. The connection dropped out but as screenshot shows, I still had an EDGE connection. I though SafeSky could use this - any ideas why Ive got a dropout?

As far as I can see and in my humble opinion, SafeSky uses UDP instead of TCP as the so-called very lightweight protocol. Unfortunately not small enough for an Edge connection. Here in Belgium I can’t connect via Edge either. The 4G connection is SafeSky’s weakness and remains a “Better than nothing” solution!