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 as anonymous. Most browsers allow these cookies by default, but some do not. Additionally, students may have manually configured their web browser to disallow third-party cookies. If you find that your students' results are being listed under 'Anonymous' in the YuJa GradeBook, the student(s) may need to allow these cookies in their browser settings, then take the quiz again.
For more information, please see the following articles from YuJa support: