Update 6/18
10:00 PM EST - Amex systems have mostly recovered from the outage. Offer syncing and activation is functional as long as you can view offers on your Amex account.
10:45 AM EST - Amex is currently experiencing widespread outages related to card offers. Offer syncing and activation features will begin working again once they have resolved the issue.
Note: This feature currently only works on desktop browsers.