ARCGis FeatureLayer not visible on version 3.2+

[RealzahAbbas]

I have a system which is currently implemented in arcGIS version 3.18 however, when upgrading to version 3.2+ the feature Layers are no longer visible.

They become visible when changing it to a ArcGISDynamicMapServiceLayer however, then the info window is then not visible with the dynamic map server.

Did anyone have this issue before?

var fLayer = new FeatureLayer("https://..../MapServer/0", { mode: FeatureLayer.MODE_ONDEMAND });
   map.addLayer(fLayer);