Overcoming fatal errors in Gromacs

GROMACS version: 2021.4-2
GROMACS modification: No
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I ran the command for protein topology ’ gmx pdb2gmx -f modified.pdb -o protein_processed.gro -ter ’ by the use of CHARMM all-atom force field and selected 5ter and 3ter as terminus types and getting the error

Fatal error:
Atom C7 in residue DT 1 was not found in rtp entry DT with 30 atoms
while sorting atoms.

how to overcome this ?