Ring Intercom and Videx 3171 Speaker Feedback

Hi AllReceived the intercom a couple of days ago which was great given it was not supposed to launch until the 1st.Setup was really straightforward however I have an issue I just cannot solve.I have a Videx 7131 intercom in my apartment which requires the B wiring and two wires into "L" & "-" which was straight forward. Checked and rechecked connections and all good to go.Started the setup and the intercom connected no problem, went outside to "dial" my apartment but when I tapped the app to say I had dialled (could hear my buzzer going off) but then just got a high pitched loud hum from the speaker. Tried numerous times and even with other 3171 derivatives just in case but the same.Decided to hit I could hear the voice and re-entered my call and the door unlocked.So I now have a system I can unlock the door with, and through Alexa, however I cannot hear or talk to anyone other than hear a loud hum from the outside speaker.Any ideas or help really appreciated.Can send photos or video if it helps