Shortest path between nodes in netlogo using nw extension - netlogo

Question

I want to find the shortest path between two nodes - slocation and new-location - in a network of links
I have several slocation and new-location. One slocation for each citizen with some age, sex, and other characteristics, and one new-location for each node close to a work building.
I could identify these nodes with colors - see image.
However, I could not identify the shortest path between each slocation (for each citizen) and newlocation.
I got the following error: BUT-FIRST expected input to be a string or list but got the TRUE/FALSE false instead.
when I run these lines of code:
ask slocation
[set path but-first nw:turtles-on-weighted-path-to new-location weight]
Is this because I have several slocation and new-location?
should I introduce and foreach variable to calculate the shortest path for each citizen? I tried already only with one citizen and still this part of the code is not capable to find the path
I think the error is that the nodes slocation and new-location are not connected with a single link. The citizens have to select the shortest path created by links connecting these nodes to reach the new-location. Someone knows how to do this?
Here, it is my other part of the code:
breed [citizens citizen]
breed [nodes node]
links-own [weight]
to go
set-timekeeper
ask citizens
[find-day-activities]
end
to set-timekeeper
tick
if (counter = 2) [set timekeeper 2] ;From 7:00 AM to 9:00 AM
end
to find-day-activities
if (timekeeper = 2) [Do_7AM_9AM]
end
to Do_7AM_9AM
if (sex = 0 and age = 1 and employment = 0 and household-size = 0)
[shortest-distance]
end
to shortest-distance
let slocation min-one-of nodes [distance myself]
ask slocation [set color yellow]
let new-location one-of nodes with-min [distance one-of workbuildings]
ask new-location [set color blue]
ask links [set weight link-length]
let path nobody
ask slocation
[set path but-first nw:turtles-on-weighted-path-to new-location weight]
ask turtle-set path [ set color yellow ]
end
If there is any question about how I create the road network from a shapefile, this is the code:
to make-road-network
clear-links
let first-node nobody
let previous-node nobody
foreach gis:feature-list-of roads [ polyline ->
foreach gis:vertex-lists-of polyline [ segment ->
foreach segment [ coordinate ->
let location gis:location-of coordinate
if not empty? location [
create-nodes 1 [
set color green
set size 1
set xcor item 0 location
set ycor item 1 location
if first-node = nobody [
set first-node self
]
if previous-node != nobody [
create-link-with previous-node
]
set previous-node self
]
]
]
set previous-node nobody
]
]
ask links [set color red
set thickness 1]
end