I have attached a following sketch file. The sketch is closed, but it's not being extruded in Creo. Dont know what is the issue.
I tried to extrude the sketch as surface and it works! but if you extrude the sketch as a solid part maybe there are too small elements.
Try to extrude it in the first way and then solidify it.
Extruding but as a sheet
reason:too small sketch ,
reason: Overlapping sketch