From IEEE:
Due to scheduled maintenance, IEEE Xplore users may experience intermittent access issues from 2:30 PM – 4:30 PM ET (6:30 – 8:30 UTC) on Friday, 21 September. We anticipate that the site may be unavailable for a portion of this time. We apologize for any inconvenience and thank you for your patience as we work to continually improve the IEEE Xplore experience for all of our customers and users worldwide.
IEEE Xplore downtime Friday afternoon Sept 21st
September 20, 2018