Out of market sales

I am brand new to Offerup and don't know all of the protocol but I'm kind of approaching this like Marketplace so correct me where I'm wrong.

I found two similar items in two different markets that I am interested in however I would need to work out a deal for shipping. No big deal if they are unwilling but it would be great if they are good with it. I reached out to each of them about my interest and asked about the shipping and I am getting no response at all. One of them I actually asked a question first and the message was seen and responded to in minutes but as soon as I asked about shipping it just goes dark.

I realize they might think I'm scamming or something but what makes me wonder is that the message status still shows delivered and not read. It makes me wonder if Offerup isn't blocking my message. I also tried to message them from their profile and I still get nothing. Am I breaking some sort of rule here I'm not aware of?