Update:
Multiplayer LAN Test - Finally Successful 
Test made with 3 PC's in LAN
Device 1 : Cable PC core i5 Win10 High Powered with SSD
Device 2 : WiFi Laptop core i5 Win10 Medium to Low Powered with SSD
Device 3 : Cable Laptop core i3 Win7 Very Low Powered no SSD
Network discovery must be turned on first, then once in the game the user can host in a few clicks or play by entering the host IP address.
The configuration used is probably a very common one, as set out below.
Router IP Address: 192.168.0.1
LAN IP Address: 192.168.0.2 (First PC in LAN - Usually the host PC)
LAN IP Address: 192.168.0.3 (Next PC in LAN)
LAN IP Address: 192.168.0.4 (Next PC in LAN)
etc...