At 11:00AM Monday, July 16th Canvas Support announced a maintenance they must conduct on July 30th @12:00AM. Their original message follows.
Canvas Status Update
Scheduled Attendance (Roll Call) maintenance on 7/30/2018 at 9:00 PM PST (12:00 AM EST)
We’ll be performing maintenance on the Attendance (Roll Call) tool in Canvas on Monday, July 30th starting at 9:00 PM PST / 12:00 AM EST. Your users will not be able to access the Attendance interface to take new attendance or generate attendance reports for up to an hour during this maintenance event.
Please contact your Customer Success Manager if you have any questions or concerns.