I will take a guess, but would not rely on it.
I don’t think IRS hands out a new CNC every year without being asked by tax payer for CNC
So maybe client just asked for CNC status for each of those years, and IRS never came back to review her financial status. Check with client, and see if she did it or someone else.
If you are considering OIC, I think first that comes to mind, determine RCP.