Tegui 374200 T-71E - Issue with RING Intercom – Cannot Hear Callers on iPhone

Hello, I recently installed the RING Intercom with my TEGUI intercom (model 374200 T-71E) after confirming compatibility through the setup process. The installation went smoothly, and most functions are working as expected. However, I’m experiencing one issue: when someone calls from the street, I cannot hear them speaking through my iPhone. Everything else appears to function correctly. Here are the current wire connections based on the app’s instructions: C2 (brown) → 5 (Speaker) C3 (black) → 4 (Microphone) C4 (white) → 2 (Common ground) C5 (grey) → 3 (Door release) C6 (purple) → 1E (Call) I’ve also confirmed that the RING app has microphone access permissions enabled on my iPhone. Could you please advise what else I might need to configure or check in order to hear audio from the street on my phone? Thanks in advance for your help.