Ever get blocked on EBAY?
Well here's a new one. I bought a sample 4 x 6 plastic bag on Ebay to see if they'd fit a 1/43 model. The seller left a good review, when I received the package I left the seller a good review. When I tried to buy 100 bags I get a message that the seller will not accept any offers from me.
Very odd, perhaps an error on the sellers part? Go back to the original listing page and try the 'send seller a message' option.
I agree with Mark: do message the seller.
I started selling again on eBay this past December. While I often purchase, I hadn't sold on eBay since 2011. In looking over my seller account, on the page where you can block specific eBay ID's, a seller can set several "Buyer Requirements". Perhaps you've slipped into one of the stipulations the seller has set inadvertently (I've been halted at Checkout because of my PO box address). Maybe the seller has adjusted their "Requirements".
I used to sell on eBay on behalf of my last employer. They sent me to (maybe the last) eBay Live! two-day event/seminar held in Boston in 2007.
Here's a photo of me with eBay's Jim "Griff" Griffith:
Marlborough, Massachusetts USA