Thanks for the info. The A1143 is at least 7 years old and as much as 8+ depending on when the product was originally sold.
Apple officially lists this product as Obsolete, so they will not provide any help on this model, even if you are willing to pay them.
If you have purchased this product recently, and have the option to return it for a refund, this is what I would recommend.
Otherwise, if you want to try to get it working, you will need to use an older Mac or PC.....as I mentioned in my last post.....to update the firmware on the AirPort Extreme. When (and if) this works, then you will be able to administer the product with your current Mac.
It's a real stretch, but if you live near an Apple Store, they might have an older Mac on hand that could be used to update the AirPort Extreme so that it would work with newer Macs.