The remote host appears to be running SIP. SIP itself is not vulnerable to Log4Shell; however, the SIP application could potentially be affected if it attempts to log packet data via a vulnerable log4j library.
A negative result from this plugin does not prove conclusively that the remote system is not affected by Log4Shell, only that any scripts the SIP proxy may be running do not create the conditions that are exploitable via the Log4Shell flaw.
Binary data log4j_log4shell_sip_invite.nbin