It is probably because you have the Ignore local traffic within the LAN option on. In this mode all data is processed by a special driver that filters out LAN traffic. You can either turn this option off, or try the latest NetWorx version (which is free trial for 30 days) as the driver received a number of updates during the years since version 5.5.5.
If you do decide to try the latest version of NetWorx, you can back up all your settings and records via Usage Reports - Backup, so you could easily go back to the free version 5.5.5 if you wish to do so later.
Generally, if you use the latest Windows, it is better to also use the latest versions of other software with it, especially when drivers are involved.