Why electronic convergence not happening within NELM

[KK]

Hi

most of the times, in my recent geometry optimisation of nanoparticles linked to ligands, the system is not happening electronic convergence within NELM.  even if i increased to very high value, say for testing 300 or more.

i checked nearest neighbor atoms and adjusted manually, tried BMIX, AMIX values variation.  in few cases changing ALGO has helped but in other cases, NO.

What could be a summarised reason for this? did anyone faced this type of issue before?

Regards