eBay is questioning me- and have blocked me from selling because they need authenticity.
Have they removed a listing for the item or are you just restricted and limited, perhaps because you have other designer items listed?
These are important questions and depending on your answers, there are different steps to take.
If your limited, you can try to appeal and have the limits lifted or you can wait out the 30 days until you can list more items.
If the listing was removed as fake, you might want to consider a professional authentication to submit to ebay. Receipts aren't necessary nor considered a proof of authenicity since they can be faked and/or genuine receipts can be used to "prove" authenicity of a fake.