But I get the following error despite using the right number of hydrogens.
Error: Semi-empirical geometry optimisation failed. The most likely cause is that either: (1) the geometry was inappropriate; (2) the number of hydrogen atoms or the net charge was inappropriate. Details: *** FAILURE TO LOCATE STATIONARY POINT, SCF HAS NOT CONVERGED (seems to only fail on step 1)
What does it mean by inappropriate geometry? I have tried to address the steric clashes by flattening the whole polymer from a curled conformation. But both of them result in the same error. However the same structure would process easily without the benzene rings and -CH3 group in their places. What am I missing?