I will assume that you have created a board outline in CircuitStudio that shows up in the workspace and also the 3D view. This outline is 'internal' to CircuitStudio and you need to generate a drawn outline for output to your Gerber files. Typically the board outline will be a drawing on the Outline layer and you can use the existing board shape to generate the drawn outline using Home > Board Shape > Generate Primitives From Board Shape. Once you have the outline then it can be included as a separate Gerber output or merged into every output (see Project > Generate Outputs > Gerber Files > Configure).
This outline is 'internal' to CircuitStudio and you need to generate a drawn outline for output to your Gerber files.
Hmm. It's very important information for me.
I copied board outline to Keep-Out layer(and existing mask shape has deleted from here with a small scheme).
And, I found a board outline in GKO layer at external gerber viewer.
I was able to create a decent gerber data. Thank you very much.
Just one additional note: While using Create Primitives From Board Shape, the "Outline" layer is not one of the choices in the dropdown. It is called "Mechanical 1". This is rather confusing until you realize from Gerber Files Configure... that "Outline" is the file extension and not the name of the layer. But on the bottom of PCB editor, "Outline" is the layer name. So this is just another example of simple GUI mistake. Personally I would like it called "Outline" layer and file extension everywhere.
I designed 2 Layer PCB and am using a Keep-Out Layer for mask from both-side copper pour. Of course, PCB outline is determined on CircuitStudio.
FusionPCB recommend to output GKO as PCB outline. Another factories recommend to output GM4.
However when I checked at gerber viewer, GKO includes mask shape without PCB outline.
Should I add line manually along to PCB outline at Keep-Out(or Mechanical 4)? Or, CircuitStudio generates PCB outline data automatically to other file?