I would fight the charge with the credit card company also sending them all the documentation and, especially the refusal of refund from Poshmark. Unfortunately for this case, Poshmark is very seller biased particularly if the seller followed all of their guidelines.
I did have a case where someone shipped me a fake Marc Jacobs dress. They were not going to refund my money after I sent them pictures of the inside seams where it was obvious that it was made by a home sewer to anyone with a set of eyes, in addition to the label being completely fraudulent and not what was displayed in the picture. I ended up emailing them three separate times, each time more angry than the last. After the third email they finally said to send the dress to them and they finally gave me a refund but it did take all of the emails. You might want to try more emails to customer support even though it seems like you're repeating yourself. I'm sorry this happened to you, that really sucks and yes the seller is insane to send a watch in that type of packaging
I did have a case where someone shipped me a fake Marc Jacobs dress. They were not going to refund my money after I sent them pictures of the inside seams where it was obvious that it was made by a home sewer to anyone with a set of eyes, in addition to the label being completely fraudulent and not what was displayed in the picture. I ended up emailing them three separate times, each time more angry than the last. After the third email they finally said to send the dress to them and they finally gave me a refund but it did take all of the emails. You might want to try more emails to customer support even though it seems like you're repeating yourself. I'm sorry this happened to you, that really sucks and yes the seller is insane to send a watch in that type of packaging