Localisization of windows ( German ) leads to an wrong format in s2p export. Decimal has to be '.' but is changed due to German windows Version into ','. This cannot be imported since it is not according to Touchstone File Format.
Example :
! 23.03.2020 08:24:54
! Ref Plane: 0,000 mm
# MHZ S MA R 50
!
100,0000 0,98878 -48,25 1,25E-3 34,79 1,248E-3 35,24 0,98802 -47,78
100,2000 0,98856 -48,40 1,281E-3 33,01 1,229E-3 32,06 0,98792 -47,92
Should be:
! 23.03.2020 08:24:54
! Ref Plane: 0,000 mm
# MHZ S MA R 50
!
100.0000 0.98878 -48.25 1.25E-3 34.79 1.248E-3 35.24 0.98802 -47.78
100.2000 0.98856 -48.40 1.281E-3 33.01 1.229E-3 32.06 0.98792 -47.92
Also I think it schoul be in GHZ not in MHZ. Matlab will accept it in MHZ but qucs expects GHZ