Getting fatal error for hetero atom

GROMACS version:2020.5
GROMACS modification: Yes/No
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Hi I am getting fetal error message as below when I prepare topology for my protein
“Fatal error:
Atom CA in residue CA 1 was not found in rtp entry CA with 68 atoms
while sorting atoms”
I ran it in CHARMM36-feb2021 version
Could you please help me to solve this error? I have two CA in my protein