I could get the SCF converged with graphene2.py and graphene2_scf2.py.
Although I've changed several parameters in order to reduce calculation cost, changing twoProbeAlgorithmParameters() would be the most important for better SCF convergence.
By the way, Can you access the latest version(11.2.3)?
If so, I strongly recommend that you use ATK 11.2.3 because a SCF convergence is more stable and an accuracy is improved.