What is the exact reason for WebRtc setRemoteDescription: "Failed to set the ssl role for the channel"?

Question

When I want to establish a WebRtc connection, I get the following error (despite the call: RTCInitializeSSL ();):

setRemoteDescription Error Domain = org.webrtc.RTCPeerConnection Code = -1 "Failed to set the remote sdp response: Failed to juggle the transport description: Failed to set the ssl role for the channel." UserInfo = {NSLocalizedDescription = Failed to install remote sdp response: Failed to load transport description: Failed to install ssl role for channel.}

Do you have any idea why?