We were recently testing out the RealPresence app for iPhone (basic mode), dialling in to an RMX 2000 via a VBP-E using the format ipaddress##conference_ID. This worked fine from the UK, using both Wifi and 4G.
However, our colleagues in Sweden wer unable to dial in. They had the same app, the same iPhone and the same settings. Their 4G was provided by 3.
When they tried to dial in, I saw the call appear as connected on the RMX. After a second or two, it showed the 'Connected with problems' message, and then dropped altogether. The VBP shows the call coming in, the message 'Bi-directional media channels established' then the message 'Call terminated by destination'.
I can see no difference between the calls from the UK and Sweden, other than geography. Any ideas as to what happened here, or what troubleshooting steps I ought to use?