I am unable to sign in to the ExportPDF service.

I have purchased a subscription to the ExportPDF service through the Adobe web site. I have checked and the subscription is current with the latest payment taken from me on January 9th of this year. I cannot sign in to the ExportPDF function through my Adobe Reader XI Tools ribbon at the top right hand side of the screen. I get an error message which reads, "A network error occurred while attempting to sign in".

What can I do?