is this a piping or frame component, or a "simple" part with a sweeping feature?
If it is an assembly with pipe or frame then you can turn in the center lines as option in the view properties.
If it is a single part YOu can retrieve center lines with the "Automnatic Centerlines" function
Left is a single part and and the right hand You see an assembly with a frame
OK, I have an assumption.
Suppose You have a single part where You used a sweep command to extrude the "pipe"
Further I suppose that You have set the sweeping options to "Fully Merge"
This will create b-spline surfaces rather than cylinders and torii.
And for them no center lines could be created automatically in draft.
Change this option to "No merge" and You will succed successfully