How to fix the error: unable to find mass for n3, when using msi2lmp to convert Materials Studio structure to LAMMPS input data?

I have prepared and equilibrated a cross-linked epoxy system of DGEBA and TETA in Materials Studio using COMPASS forcefield. I now want to obtain an appropriate LAMMPS input data file of this prepared system using msi2lmp. I have been using class 2 frc compass_published. but I am getting the error: unable to find mass for n3. I have no idea how to fix this error. I would appreciate any help on this matter.