I have generated multiple coupon codes inside same rule. However one of coupon code is not working. I tried to add that coupon code and it was working but suddenly it stopped working. I also checked in database and it is not used. It is also not expired. All other coupons are working fine under same rule. Is it stored inside customer session or something like that  ?

I have generated multiple coupon codes inside the same rule. However, one coupon code is not working. I tried to add that coupon code and it was working but suddenly it stopped working. I also checked in the database and it is not used. It is also not expired. All other coupons are working fine under the same rule. Is it stored inside a customer session or something like that?