Via their support:
“Our servers were up and running consistently the whole day yesterday. BUT, several other academic library customers along the East coast reported a brief drop of service simultaneously around 4:45pm Eastern time. We worked with them through our routine support chat and email channels, and they all seemed to spontaneously recover after a couple of minutes with no real actions on our end.
We suspect this was some sort of regional network problem since our servers were fine throughout, and it didn’t impact everyone. Our support chat line stayed up and busy throughout, and we’re on the east coast ourselves, with our support chat running on the same servers as our customer services.”