There is a known issue with YuJa quizzes embedded in Blackboard where some student responses are saved under Anonymous rather than the student's name. This is a result of a web browser setting that disallows third-party cookies. Essentially, the web browser does not allow Blackboard to tell YuJa which student is taking the quiz so YuJa just labels the results under Anonymous. Most browsers allow these cookies by default, but some do not. Students may also have manually configured their web browser to disallow these cookies. If you find student results being listed under Anonymous in the YuJa gradebook, the student may need to allow these cookies and take the quiz again.
For more information, please see the following articles from YuJa support: