ERROR 1 [file topol.top, line 62]: No such moleculetype CL

[TreeLife]

This seems like a common error.
I remember seeing it somewhere:

Gmx genion -s proteinions.tpr -o proteinions.gro -p protein.top -pname NA -nname CL -neutral

Thanks a lot for the guidance, I added CL to ions.itp file inside charmm and got the results…:)