When setting up a Turnitin Assignment, it is important to ascertain what type of assessment has been set for the module for you to then be able to select the correct set-up. Please read Before you set-up a Turnitin Assignment for guidance.
In addition, although Turnitin can accept a variety of file formats, submissions must meet a set of requirements for Turnitin to be able to return a Similarity report.
Since our move to Blackboard Ultra and specifically October 2022 any new Turnitin Assignments that need to be created in an Original Blackboard are created via the newer Turnitin LTI.
Please see: How to set-up a Turnitin Assignment in Blackboard Original using the newer standard of integration called LTI (Learning Tools Interoperability)