Revocation of cancelled GST registration: one-time opportunity to apply subject to furnishing pending returns and subsequent filings. Applications for revocation of cancellation of registration under section 29(2) are permitted only after all returns due up to the date of cancellation are furnished and amounts paid; where cancellation is retrospective and the portal prevents post cancellation filing, an application may nonetheless be filed provided all returns for the period from the effective date of cancellation to the revocation order are filed within thirty days of the revocation order.