Mistaken Copywrite Infringement for Vintage Item

[VintageButtercup]

I received a copywrite infringement notice for an original vintage magazine advertisement from 1969. In the email I received from Etsy, there was contact information from the company making the complaint.  I sent an email to the person listed and the email was kicked back to me as an unknown email.  I then tried contacting Etsy, but all they did was respond saying that because it was a copywrite infringement I needed to contact the person making the complaint.  I'm just going in circles.  Any ideas on what to do next? I've had a vintage shop for 14 years and this is my first mistaken infringement notice.

[FallenAngelBrass]

Could also be a trademark infringement of the brand name and possibly logo.   Copyrights expire but a trademark can be indefinitely renewed.  For example, you cannot legally sell vintage Vogue magazines because "Vogue" is a live trademark and (I believe) it's owned by Condé Nast.   Many vintage magazines are legal to sell because their names and logos are long dead trademarks, but there are some (usually successful) magazines that still have live trademarks.  All of this applies to the ads within magazines.  Not all vintage ads are OK to use in art or reproductions to sell.  Some are still under copyright for their artwork and some are still live trademarks for their brand name. 

[VintageRescueSquad]

The only way to resolve this is to contact the complainant. Although the email bounced back, if it is from a company go through their main phone or email.

[BagmakerSupply]

@VintageButtercup: "I received a copywrite infringement notice ..." Are you sure it was a copyright infringement and not a trademark infringement? For copyright, you only need to file a counter claim with Etsy (contacting copyright owner is not required). For a trademark infringement, you need to have the trademark owner rescind the infringement claim.