Outline layer file gerber

I have created the file gerber for my PCB to realize perhaps in NextPCB.
I have sent the file gerber but the supplier said that the outline layer file gerber is missing.
In the annexed screenshot you can see what I have selected.

Can you indicate me what I have to select to obtain the outline layer file gerber?
tank you

For the edges of the PCB you have to draw lines on the Edge.Cuts layer:

They are normal graphic lines and arcs from the Pcbnew / Place / Line menu. Do not use Polygons on Edge.Cuts.

It is important to realize that the line and arc segments mus form a closed shape. The easiest way to do this is to use a coarse grid (For example whole millimeters). You can also snap line segments to each other by dragging a line endpoint to another line endpoint. When a snap point is recognized, an additional small circle is drawn around the crosshair mouse pointer.

I have realized the line around the PCB using “add graphic lines” and Edge.Cuts was selected, but when I have generated the files gerber I didn’t obtain the “outline layer file gerber”

Lines on Edge.Cuts are yellow (by default, and also i your settings)
The line I assume should be on Edge.Cuts is grey.