Update: Looks like these scores are showing up as normal again.
American Express is no longer offering cardholders free FICO scores. Unfortunately cardholders are now offered access to American Express MyCredit Guide instead. American Express MyCredit Guide was launched in May 2018 and is offered to all consumers, even if they don’t have an American express card. The score they provide is VantageScore 3.0 and is powered by TransUnion credit reports. VantageScore isn’t as useful as most lenders use FICO scores to determine credit eligibility. American Express first started offering cardholders free FICO scores in 2014 in a trial program, before it was widely rolled out in 2015.
Hat tip to reader PT

