GSTR 3B & GSTR 1 Filled nill even after sales what to do now?

ONE ON MY CLIENT HAS NOT FILED RETURNS FOR MANY MONTHS SO HIS GST NUMBER IS CANCELLED IN NOVEMBER 2019 ..NOW I HAVE FILED ALL RETURNS TILL SEPTEMBER AND FOR OCTOBER THERE WAS PURCHASE AND SALE RESPECTIVELY BUT HE HAS NOT PROVIDED ME BILLS FOR THAT NOW AFTER FILING REVOCATION OF CANCELLATION OF REGISTRATION APPLICATION THE GST COMISSIONER FOUND THAT THERE WAS PURCHASE OF AROUNF 5 LAKHS IN OCTOBER AND I HAVE FILED NILL RETURNS FOR THAT MONTH . I AM QUARTERLY FILING GSTR1 FOR HIM....NOW THE COMISSIONER TELLS TO PAY TAXES FOR THE SALES FIRST THEN HE WILL ACTIVATE MY GST.. HOW THIS IS POSSIBLE ....PLEASE HELP   WHAT TO DO NOW?