Hi there, which Revit do you use for this script? Probably in Rvt 2025 MEPower package won’t work. If that’s the case, try OpenMep.
If it’s Revit 2024, or earlier
Please make sure if your pipe type, which you’re using, have set up routing preferences (elbows, tees, transitions etc.). And make sure diameters in routing preferenses cover DN 20 mm size.
Also it will be useful to see a screenshot of pipes, which are created on previous step.