Apple serial number

[rouderon]

I'm looking to buy a 5th gen AirPort Extreme off of craigslist and asked the seller to fw me the s/n. When I tried to check it on the Apple support page, it didn't return any info whatsoever. Does this mean I have an incorrect s/n or that it is out of warranty?

The message I get is: 'We're sorry, but there are currently no solutions available in your location.'

And, the location is set to US: English