The latest VirtualDJ version requires "session name" on the VirtualDJ broadcast settings for the direct live stream on shoutcast v2.5 and v2.6. If you leave the "session name" empty, it will fail to connect without any error.
If you are streaming live by using VirtualDJ without AutoDJ to shoutcast v2.5 or v2.6, make sure to enter "session name" in the broadcast settings of VirtualDJ.