Lamilya Toxx

Hi, I'm new to selling items on the MP. I have a huge amount of gacha items I want to try selling (for the same amount as or less than what I paid for them). The permissions are set correctly, they're transferrable and modifiable. But for some reason, every time I try to send them to the MP, I get an error message that it's an unsellable item and that it's probably a permissions issue. I've sold them at yardsales in the past with no problem, I'm just trying to avoid paying rent this time. I would really appreciate any help figuring out what I'm missing (it's probably something totally obvious, lol). Thank you!