If your bank account has been frozen because you haven't filed your GSTR-3B return, it's important to understand the process for getting it reactivated. While account seizure for a single month's non-filing might seem unusual, you should first contact your bank for the official reason and a copy of the seizure notice from the GST department. Once you've filed the outstanding GSTR-3B return, formally request the release of your bank account by providing proof of filing.
17 April 2020
I don't thing they seize your account due to non-filing of GST Return, but still here is my suggestion
GST Officer must have sent you notice before seizure of accounts, if not then ask your banker for the reason and copy of letter of seizure of bank account they received from GST department.
File your GST return and then write letter/Email to your office for release of bank account (attached GSTR 3B Return filed acknowledgement)