Turnitin have posted the following maintenance advice.
"Turnitin services may be unavailable during a scheduled maintenance period on Sunday, March 8, 2015, from 12.30 am to 4.30 am
An announcement will appear for users within Turnitin at least 1 week in advance of when the system will be unavailable for this scheduled maintenance.
Instructors are encouraged to modify assignment due dates either before or at least several hours after the scheduled maintenance window.
Thank you for working with us as we improve Turnitin.
The Turnitin Team"