I am also impacted by this and have been directly connected to our AMEX account for over 3 years and as of February 2019 it stopped working.  I was able to force it to work initially be disabling online banking for the AMEX account and then reconnecting but that now is also giving me either ERROR codes 1001 or 500.

Thank you Nutmeg for the manual work around but would definitely hope that the real fix would be forthcoming soon.