Keyboard issues on Apple keyboard wired

A wired keyboard should be plug-and-play. You've tried more troubleshooting than I would have, before deciding that the keyboard has an electronic issue. Perhaps water had been spilled into it at some time in the past? Electronics can develop problems in storage, depending on the ambient temperature & humidity where packed away, like a hot attic or humid basement. I'd request the refund and look for another keyboard. A gently-used keyboard usually presents with minimal wear on the alphanumeric characters printed on the keys and a space bar without a shiny, wear spot from repeatedly tapping on it. The price that you paid seems high, unless it was one of the Apple keyboards with a clear acrylic back. If it's one of the old beige keyboards, I wouldn't have paid that much unless it were new-in-box, BUT that would have been 15 or more years ago. Although an old, but new-in-box keyboard stands a better chance of functioning normally when connected (depending on storage conditions), there's always the unexpected hiccup that leaves you wondering what happened.

demdi75 wrote:

another keyboard

plugged in works fine.

That alone is enough for me to indicate "refund" is the way to go.

Welcome!

It is hard to help without more details. Apple made several wired KBs with numpads going back to 1987. Some can be opened for evaluation and service, others not.

Please find the model number—usually on the bottom of the board—and post it. Model numbers will begin with either "M" or "A" followed by four digits.

Examples: A1243; M2452

If you cannot find a model number, snap a picture of the board, top and bottom, and post it in a reply to you initial question using the "Image Insertion" tool in the toolbar:

That—an A1243— is one of the models that cannot be opened for repair. It's a good board—I think I have three 🙄—but you need to be sure that it is 100 percent before making the deal.