I have had similar experiences, sellers simply don't want to do anything other than place an ad expecting gear to simply go away by itself? I have had people not wanting to answer questions, insisting on pick up only, refusing to pack stuff, insisting on only one method of payment, refusing to hold something long enough for me to get there, you name it, just the way some chose to operate, I simply move on.
There are many great sellers out there who are a real pleasure to deal with, I have been fortunate to run across several and have acquired some excellent pieces.
There are also many horrible platforms that are a real hindrance to a sale, often preventing it outright. I had made a deal on this site for a piece and during conversation an extra piece was offered that was not listed, all communications were blocked so the sale died, it was suggested that we were trying to share contact info to deal offsite which was not the case.
I have also had offers blocked on another site as they believed my cell phone number was actually a landlines, faulty research on their part but killed the sale. I was even blocked on one site as the moderator did not like my name, thinking it was fake. The odd thing on that one was I had not been asked for a name, the site scraped it from a social media platform which sported a screen name.
So many obstacles to prevent simple transactions from occurring?