mp.second_order cannot generate second-order units

[sgrlifire]

Why can't I generate the vol file of the second-order element after using (mp.uselocalh = 1;
mp.elementsperedge = 2.0;
mp.elementspercurve = 2.0;
mp.maxh = 10.0;
mp.grading = 0.2;
mp.closeedgeenable = 0;
mp.closeedgefact = 1.0;
mp.optsurfmeshenable = 1;
mp.second_order = 1; )

[sgrlifire]

ng_occ.zip
Using this example, add mp.second_order = 1; Second-order elements cannot be generated