If I double-click the name of the extension, nothing happens. Same for the curve centerline extraction module. How can I load these modules? I have tried installing-deleting the modules and slicer itself, but it does not help.
As for “Curve centerline extraction” module, it is a helper module, that combines and automates a segmentation process relative to an arbitrary curve, followed optionally by centerline extraction. It has a dependency on ‘Slicer segmentation extra effects’, that you should install separately from the ‘Extensions manager’.
Select ‘Centerline extraction’ module instead. If this one does not work, there’s another problem.