Response Rate

[BootTiaras]

I got dinged on my star seller account after buying from another seller.  I received a download code that a didn’t need to and was unable to respond to.  I don’t see why me as a buyer can affect my star seller number. 

[CraftyCornishMaids]

Etsy says to respond to each new message thread, or mark as spam, whether from buyer or seller

So that's what you have to do.

etsy handbook on star seller

https://help.etsy.com/hc/en-us/articles/4403058372503-How-to-Become-a-Star-Seller?segment=selling

extract....

The Message response rate only applies to the first message in a thread. Initial messages from both buyers and sellers on Etsy are counted towards the Message response rate. 

[BagmakerSupply]

@BootTiaras: "I don’t see why me as a buyer can affect my star seller number." Because Etsy says so. As it says right on your Star Seller page and elsewhere, you need to reply to (or mark as SPAM) the FIRST message of EVERY NEW INCOMING THREAD within 24 hours. It does not matter who sent it, the subject matter, if it is a duplicate or blank or anything else.

[OmasFabricStash]

Sellers are not dinged for buying something on Etsy. They are dinged for not responding to a message or not sending it to spam. Who the message is from or the reason it was sent doesn’t matter at all. It could be from a buyer asking a question, a seller you just bought from, or Aunt Peggy saying hi. For every message you receive you need to send it to spam or respond to it. The reason for answering all messages is simply because Etsy said so. 

[JMOldeVintage]

@BootTiaras  - Yes, all messages sent require a reply, whether you are the buyer or seller.

Though I'm a bit confused. You say  "I received a download code that a didn’t need to and was unable to respond to."

What was the reason that you could not reply? Was the message truly from the shop you purchased from?
Or was it some sort of scam/spam message & Etsy eventually banned the user due to their sending scam/spam messages?

If the answer is "yes" to the second question, if you still have access to this message mark it as Spam. It really is spam & needs to go there. Your stats should eventually reset.