SERVER_ERROR NO: 6 MSG: Unknown access key

I’ve successfully installed and activated your plugin on three sites, but this one won’t accept the access key. I get this error:

SERVER_ERROR NO: 6 MSG: Unknown access key, check if the key is correct

This site’s email is hosted at GoDaddy, so I imagine that’s the culprit, as my other sites are hosted elsewhere.

The page I need help with: [log in to see the link]