Igst issue

I have sold product in Assam In A/C Year 2017-18 & I have entered them in Export Invoice,i.e.,Table No. 6A of GSTR-1.But now a mail has sent by portal which says that those invoices have not transmitted in ICEGATE so it can not be validated & nw the system uses ledger based approach to validate it.But now my problem is they donot support the return section.All dashboard appears but return dashboard does not appears.I have filled the GSTR-1 bt cannot filled the GSTR-3B.My question is how much time take this validation?Can I filled GSTR3B before or on 20th september?What can I do?Please give me mail of GST portal.