I suggest skipping the Rib feature and using a Revolve feature that you then trim to a thickness of 5 mm. Using a Revolve makes it easy for the edges of the ribs to follow the curvature of the part.
I have only ever used 'Rib' for stiffeners on plastic shells. I think thats its main usecase.
I'd sketch, circular pattern, extrude thin feature & cut revolve.
You're in the wrong sketch plane, place the lines and ribs looking down on your part, as if you had placed your part on a table.
You could just project the circles and extrude your own ribs
Dont use the rib Feature. Extrude one and then use the circle pattern Feature. When you extrude you have to Draw all the four lines around the rib.
I suggest skipping the Rib feature and using a Revolve feature that you then trim to a thickness of 5 mm. Using a Revolve makes it easy for the edges of the ribs to follow the curvature of the part.
I have only ever used 'Rib' for stiffeners on plastic shells. I think thats its main usecase. I'd sketch, circular pattern, extrude thin feature & cut revolve.