SIP via Transport Layer Security (TLS) is encrypted and decrypting is necessary to interpret the SIP flow.
The VoIPAnalyzer Tool currently does not support the decryption of SIP via TLS.
TLS can be decrypted when the TLS handshake is captured, and the certificate private key is known.
However a certificate private key is best kept secret at all times, and for sure not transferred.
In case a Wireshark contains the TLS handshake, and the TLS session keys are available (for example in a logging file) then the capture can be decrypted.