When secure calling is enabled, Twilio cannot accept calls made using UDP or TCP. Please use TLS.
Possible Causes
Media security is enabled on your SIP domain or trunk, but Twilio received SIP traffic over an insecure protocol, such as UDP or TCP.
You are using SIP registration, and are attempting to place a secure call to an endpoint where all of the available bindings were registered with an insecure protocol, such as UDP or TCP.
Possible Solutions
Please ensure your PBX or end device is configured to send SIP traffic over the TLS transport.
If you are using SIP registration, your device must be configured to register over the TLS protocol. Devices registered over insecure protocols will not be attempted for secure calls.