I've submitted my work to Turnitin, why does it say 'Processing'?  
This means your work is submitted but Turnitin is in the process of creating a Similarity Report.
The first time you submit a piece of work (and the following 3 resubmissions), it can take between a few seconds and a few hours to return your report, but it may take significantly longer at peak hand-in times. The fourth resubmitted assignment will always take a minimum of 24 hours to return a report. 
If you have concerns, get in touch with your module tutor. Occasionally the processing of the report fails and something needs to be done behind the scenes.
For further information and guidance, see the Turnitin Submission section in our Online Learning Support pages for a video demo or pdf guide on submitting or viewing grades/ feedback.