Black Market "Selling"

So I noticed someone was wanting to buy Catalytic Converters on the Black Market. After clicking on the Sell option, and then the sell option for the price, it gives me the unknown error and tells me to try at a later date. I wanted to know if this was a bug or not. I do have the Catalytic Converters on me and they are up to the sellers wanted grade as well. It also happened with loose notes earlier as well. I was able to buy things off of other people's listing and post my own buying listing, and it only seems to happen when trying to sell things to others from their listings. Unless I am missing something obvious.