Dear Junjie,
the Flair files from the Online training (FLUKA Beginner Online Training (Oct 5-16, 2020) (5-16 October 2020): Overview · Indico) are only compatible with Flair 3.
Also, please keep in mind we only provide support for FLUKA version (currently 4-1.1) released by CERN at https://fluka.cern
Cheers,
David