Hey @Felix
i have the same issue, when i upload the .zip file no outline is detected.
I made the gerber files like described here Altium Circuit Studio.
The every menu item is the same, without in the last step the Mechanical 1 is not in my list. I have Outline as Option.
In the gernerated outline file is:
G04*
G04 #@! TF.GenerationSoftware,Altium Limited,CircuitMaker,2.2.1 (2.2.1.6)*
G04*
G04 Layer_Color=16740166*
%FSLAX24Y24*%
%MOIN*%
G70*
G04*
G04 #@! TF.SameCoordinates,4F79340E-7696-4130-B975-83647B8B98CC*
G04*
G04*
G04 #@! TF.FilePolarity,Positive*
G04*
G01*
G75*
M02*