Is this a scam?

Hi! So as the title suggests, I’m wondering if this is something that is a red flag. As I said in my message, I’ve received no notification or warning that the shipping was unpaid. I would also like to mention this is the last day they have to mail this to me (Facebook market says they have till September 15th to send it and it’s currently sep 14th). I’ve never had this problem with any card of mine or with my address. I just want to know if I should jump on a refund sooner rather than later. It’s just making me suspicious because I’ve heard nothing from USPS or Facebook. Screenshot convo in the comments