In case anyone else signed up for Paperless Billing on their American Express card gets a late fee this month, there is a problem with their servers which is causing alert enrollments to fail.
Image One. I select payment due alerts, and click Enroll.
Image Two. A window pops up but fails to load properly (server reset). Going back to alerts page shows that enrolling for the email alerts failed. I tried multiple times (I'm using Firefox v22.214.171.124).
Mohini (id 79480) with American Express Online Services, confirmed that there is a server issue and I should retry in 24 hours. I did get a late fee as I did not pay on time (didn't get the usual email that reminds me to), but American Express was very courteous in reversing that fee.