it says "face or fillet/chamber does not exist"
it says "face or fillet/chamber does not exist"
It may not work since you are using face fillet. So instead try a cut extrude and then pattern that. Other option is what Krzysztof Szpakowski has suggested.
You select faces or features to pattern. Check too "geometry pattern" option.
And better is do one complete instance double arm with radius and hole and pattern it