This issue is resolved. Turnitin is reporting regular return times on Similarity reports.
A fix has been implemented and access restored to Turnitin.com and the Turnitin ICON Integration. Users may experience slowness as service is fully restored.
Turnitin plagiarism detection is down. The outage affects Turnitin.com and the Turnitin ICON integration. ITS staff are working with Turnitin to resolve the issue.