TurfsJoins pointsWithinPolygon => Need more informations

Hello !
First of all, thank you for your work!

I have a service that transforms data into geojson.
I have points and polygons. I want to check if the points are in the polygons. For this, I use "TurfJoins.pointsWithinPolygon()".
But when I pass my two FeatureCollections as parameters, it returns an empty list. Maybe I forgot something?
After several hours of searching, I decide to turn to you. I thank you in advance for your help. I code in Kotlin

class PointWithinPolygonService @Autowired constructor (val tblPolygonRepository: TblPolygonRepository, val pointsService: PointsService) {
     fun withinPolygon(): FeatureCollection {
        val polygons = tblPolygonRepository.findAll()
        val points = pointsService.getPoints()

        val pointsFeatureCollection = FeatureCollection
                .fromFeatures(points
                .filter { it.gpsLongitude != null }
                .map { Feature.fromGeometry(Point.fromLngLat(BigDecimal(it.gpsLongitude!!).setScale(4, RoundingMode.CEILING).toDouble(), BigDecimal(it.gpsLatitude!!).setScale(4, RoundingMode.CEILING).toDouble()))
        })
         
         val polygonsFeatureCollection = FeatureCollection
             .fromFeature(Feature
                 .fromGeometry(Polygon
                     .fromLngLats(polygons
                         .map {it.getListCoordinates()?.map { it -> Point.fromLngLat(it.longitude, it.latitude) } }))
             )
        return TurfJoins.pointsWithinPolygon(pointsFeatureCollection, polygonsFeatureCollection)
    }
}

Start at TurfJoins.pointsWithinPolygon and compare the supplied FeatureCollection construction with the method's expected polygon coordinates; inspect the Kotlin service code shown, especially filtering and coordinate order. Reproduce the empty result with the same points and polygons, and consider the issue done when the cause is identified and the method returns the expected points or the required input correction is documented.