what does undeliverable mean on amazon

For a number of reasons, a shipment could be returned as undeliverable: The address is obsolete or wrong. The time that the cargo is typically held by the courier before being sent back to us can vary. When placing your order, kindly double-check the address.

It may happen for many reasons like your address being outdated or incorrect.

The first reason is that the address you gave was wrong. If the package is returned to Amazon, they’ll contact you to let you know what happened. You can then try to re-send your package to the correct address.
The second reason is that your package was delivered, but nobody was home to sign for it. If this happens, Amazon will try again after a certain period of time (usually two days). If nobody’s home again, or if there’s no response from Amazon, the package will be returned as undeliverable. You can email them at returns@amazon.com if this happens to you so they can work with you on getting it back into their hands and on its way to you!