From the 13th of May if you are a first time user of Turnitin you will be prompted to accept a new User Agreement before submitting online assessments using the service. At the time of writing a copy of the full User Agreement can be found here.
If you do not accept the new User Agreement you will redirected to the Turnitin homepage instead of the assignment.
If you have already accepted an existing older User Agreement you will also be prompted to accept the new User Agreement before continuing with your submission.
You can find out more information about Turnitin on Shuspace.