Turnitin does support Student Preview submissions in Blackboard. However, when exiting Student preview, the Turnitin window covers the Exit window preventing you from exiting Turnitin.

Solution #1:

Open a new tab in your browser. Close the browser tab with Blackboard. Return to the new tab and log back into Blackboard. You will still be in the Student View, but you will be able to close out of the Student View.

Solution #2:

Click and hold the Back button on your browser until a menu appears. This is your browser history. Click on a folder or a content area other than the Turnitin assignment listed. Note that the Turnitin assignment may be listed several times. Do not click the Browse button as Turnitin will keep loading.