I often get escalation from people that have Intel vPro systems provisioned with SCCM and can not get RealVNC Viewer Plus to successfully connect to these systems.
One thing to remember is that SCCM provisons systems in a TLS mode. SCCM will push a web certificate into the firmware during the provisioning process to be used during OOB managment (like KVM or SoL/IDER). Since the web server certificate in the vPro firmware was issued to the fully qualified domain name of the vPro system, then you must also ensure you use this same FQDN in the VNC Viewer Plus app. If you only use the system name (no domain) or ip address, the Viewer console will not accept the certificate and the connection will fail.
If your ISV console is not using TLS, then you can use IP Address or simple machine name. Also, SCCM leverages Kerberos authentication. If you are logged into a system with an account that was defined in the SCCM profile with redirection rights, then your kerberos will automatically be passed through the KVM session and authenicated to the vPro System.