This behavior occurs because a valid source directory for the software, whether it be a CD/DVD/USB drive or files on a network, has not been selected. The solutions to this are listed below ordered by VLM version.
VLM 3.0 and Later
In order to create a volume license installer in VLM 3.0 and later, you must browse the folder containing the setup.exe file for the software. If you select a valid source location, the Product Name (Installer Name in VLM 3.1) field will be automatically updated. If you do not select a valid location, VLM will show a dialog saying VLM will copy the contents of the source without modification and create the installer without any additional VLM information.
Note: from LabVIEW 2019 and later, all NI installers are now based around NI Package Manager packages. You must have VLM 3.2 or later and NI Package Manager to be able to make a custom VLM installer for any software version of 19 or later.
VLM 2.1 and Previous
For VLM 2.1 and any earlier versions, you must browse to the folder containing the setup.exe file for the software to create a network installer. Only then will it make changes to the installer and create the mslsetup.exe file, which is the network installer. In most cases, the setup.exe file is in the root directory of the CD but in some cases you will have to browse to a different folder containing the executable.
Beginning with LabVIEW 8.6 (Q3 2008 Platform DVDs and Developer Suite DVDs), NI transitioned to using MetaSuite installers. Support for MetaSuite installers began with VLM 2.1.1, so if you are using an older version of VLM to create Network Installers for any software from Q3 2008 and later you will need to upgrade to VLM 2.1.1 or later.