Turnitin issued the following service announcement at 3:32pm today.
TurnitinUK experienced an outage between 13:50 and 14:55 GMT. The service is now accessible again. UK users accessing our service via an integration may have been affected over this period. Users of the Turnitin.com service would not have been affected.
We apologise for any inconvenience caused. If you are still having issues, please contact our support team at https://go.turnitin.com/e/45292/2nrSz7M-/bb4tk8/752185963
Turnitin have a twitter feed for their status ( @turnitinstatus ), or, if you prefer, you can sign up to Turnitin Status alerts. http://www.turnitin.com/self-service/system-status.html