Apple's coverage checker site seems to not like the serial number of my 3rd gen iPod

I recently bought a 3rd gen iPod and, out of curiosity, I put the serial number into the coverage checker site to see a bit more info on my iPod (really just me wanting to see when it was bought). Weirdly, though, when I put in the serial number, the site kept saying it wasn't able to complete the request. I've tried it on a few different devices but still with bad results. Any idea why the coverage checker site doesn't seem to like my iPod's serial number?