I like to know the reasons of the following error:

iSCC Total electronic Diff electronic SCC error  
1 -0.22879491E+03 0.00000000E+00 0.35364565E-08

I am working with a Coronene 7x7 structure stacked with a triazene ring. Initially, I am optimizing the system using DFTB+ methodology. What could be the reason for the failure of this job?

If needed extra information can be provided.

With advance thanks,

Keshab K. Adhikary