Looks like it's been failing for a couple of weeks now. I disconnected the account in Simplifi to see if re-connecting would fix the problem.
The sign-on popup is coming up, but when I click Sign On, I get the error: "We encountered a problem processing your request. Please try again later."
URL is: https://citiretailservices.citibankonline.com/RSauth/ob/aggregator/obsignon?siteId=PLOC_EXXONMOBIL&pageName=obsignon&langId=en_US