It says my NFT is “not open for auction”

まだ日本語では提供されていないため、原文で表示しています。上のメニューから翻訳できます。

Only collections that Creta has enabled on its auction contract can be sold here. Creta's own collections, and NFTs minted on Creta's marketplace, are enabled. Most NFTs from other projects are not.

Nothing is wrong with your item. It is still yours, and you can still send it or sell it wherever its own collection is traded.