Notice u/s 74 of cgst act, "purchase from cancelled dealer"

Dear Sir, I purchased goods during the year August 2017 to March 2018 from a supplier at that time the Supplier status was Active in GST Portal and the supplier had filed all GSTR 1, GSTR 3B and GSTR 9 for that FY 2017-18. My transaction with the supplier was completed during FY 2017-18. On 28/09/2020 i got notice u/s 74 of CGST Act to Pay the Availed ITC on such purchases along with Interest and Penalty. After receiving the notice when i checked status of my suppliers GST No i found that it has been cancelled from retrospective date of 01/07/2017 by the GST Department suo moto. Since i have paid the Value of goods along with GST to the supplier. How to deal with such a notice. Please guide me regarding the same.