Import Error - Special functions

Hi,
I tried to add special functions from the library SLATEC following the steps on github.com/NGSolve/ngs-special-functions.
I think the installation went through but I get an Import Error when I run the demo bessel.py:

ImportError: /python3.8/site-packages/ngsolve/special_functions.so: undefined symbol: _ZNK5ngfem19CoefficientFunction14GetDescriptionB5cxx11Ev

I am using ngsolve 6.2.2301,
Thank you.