Coarse grain polymer generation

I am trying to generate coarse grain polymers in lammps, I used chain.f fortran code(tools in lammps) and got a overlapping structure , to remove overlapping I tried to use soft potential with harmonic bond style and simulated it under nve ensemble . After the run if I try to switch the bond to FENE , and pair style to lj , I am getting error of bond atoms missing ,can anybody help with this ?

Please search the forum for (the many) people having reported the same error and try out the suggestions given to them. It basically means that you have some very large forces in your system due to one of multiple possible reasons.

If that does not work out, please provide access to (all) your files, so people can have a closer look.