Before you can sell you card on the market, you need to make sure the card satisfies the sell conditions.
Please refer to our FAQ: https://godsunchained.com/learn/faq
During Season 1, all Items (excluding chests and draw tickets) are usable in-game from purchase but will not be tradable or minted until the release of Immutable X, our item exchange on the Ethereum network.
If you are sure you have cards for sale, please let us know which cards you consider to be sellable, so we can investigate. Thank you