CIPC can have different devices assigned for ringer and general audio - so your speakers can ring, but then you listen on your headset for example. Check your audio settings.
Also when on a call, press the ? key twice on the CIPC display, you'll get stats and you should be able to see your RX counters. If you don't see them incrementing then you have something blocking the RTP stream -this might be a client/windows firewall, a VPN NAT issue, or a million other things.
IF rx is incrementing then you are receiving them OK, so try messing with the audio output settings or run the tuning wizard again.
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