A banner like this has been appearing, on & off, for the last 3 weeks (link, SAS) now:
The Ads Billing Console (link, simplified) was totally inoperative for the entire month of August, whether or not the banner was displayed on any given day; various other Ads Console functionalities have been intermittently unavailable - and, more-frequently, hit-or-miss on pulling data when they are functional - throughout the period.
Amazon coding at its finest.