Hi,
Can you give me more information about your code?
On my side the lan api works :
term.write(lan.getLeftSignals()) // Print the signal on term
NB:
The lan api work only on a "computer" placed on the ground (craft), not on your "personal computer" what you open from the icon at the top left.
To open a computer console on the floor, target it and use the keyboard shortcut (default: "CONTROL + Left mouse button". You can change it from the mod shortcut menu option)
You can know the list of available apis for a specific computer (personal, placeable, or "onboad"), from its console by entering: "help apis"
I think adding today or tomorrow, some examples on the use of apis lan and wlan
(They can be found here: https://github.com/Relik77/factorio_computer_core/tree/master/examples)
The examples are tested with the current version, so if I identify a problem I will fix it as soon as possible ;-)