Ring Doorbell won't connect over 4/5G EE

I am unable to answer my 2nd gen ring doorbell via 4/5G, I get the notification that someone is at the door, however when I answer, it get stuck on "activating device" and will not connect. Using a Oppo Find X3 Pro. If I am connected via wifi, there isn't any issues. I have tried my work phone on Vodafone and my wife's phone on Three, and they both connect fine over 4G. The live view will connect over 4/5G with EE. I have cleared the cache, deleted ring app, installed ring rapid, reset the ring doorbell, changed IVPv4, content unlocked on EE app and contacted ring support who claims it's a network issue, none of these have worked. Having searched the EE & Ring community support pages and spoken with the technical teams at EE & Ring there isn't a clear answer to the problem. Has anyone solved this issue?