the coupons are not working because they were for different category [toys, hobbies, goods ], your photocards were in the [books, music, games] category
I know this is an old video so you might not need this info anymore, but I live in japan and often use Mercari Japan to sell things, and I think that the reason the coupons aren't available is because of the categories! When you sell on Mercari you can set the item's category, and there's a specific "kpop" one so regardless of if it's a trading card or not, most sellers will put their kpop listings in the "kpop" category, which is why you can't use the trading card category coupons!
I am very new to Kpop. Started getting into it in 2022 and only now started to collect albums etc... So these videos are very handy for me :) I am for Europe so trading/selling options are already slim, so its nice to see the options and how it works :)
