There's a LOT of nonsense with Sovcits but you basically just need to understand a couple things. Sovcits basically believe that the government has some secret account with millions of dollars in it in your name and that there are some equally secret methods to access that money. So basically this "coupon" would try to pay for goods using that secret account, using a secret and convoluted process, and using magic legal jargon.

The bank just said, "Sorry, we don't accept whatever this nonsense is. Plz send real money."