Supply made to SEZ Unit

Mohan Bagalkot (Tax Consultant) (233 Points)

24 November 2018  
Dear Friends
I am getting email after filing GSTR3B from GSTN stating "Non -Transmission of Invoices due to -tive balance". What does it means? Unable to understand.
There is a supply to SEZ unit and shown in GSTR3B 3.1a and in GSTR1 Shown in Table 6B i.e., B2B.
Am I doing anything wrong declaration for which I am getting this email. Pls help me guys