Regarding Export of Goods

Sir,
My client have exported Goods outside India,but before reaching to the port of Impoter, Goods were seize due to importer licenses was expired.
After communication with border security forces they denied for return the goods to India. and same Goods where dumped into see.
I have raised credit note for same exported Goods in March 2019.

But in RDF 01 Statements 3 such credit notes is not reflected.

Now GST Dept have asked to pay the excess refund claimed

My question
1) When Goods are not been received back to India. whether I need to payback the tax amount ?
2) When Goods are exporter outside India and forex is not received then also I need to payback tax amount to department?

please advise me
Thank You.