LMS not reporting 'Completed' status

We are delivering e-learning content to a client using SCORM 1.2. So far, we have delivered around five modules. In all of them, the completion setting is the same: the course is marked “Completed” once the learner has viewed 100% of the slides.

All previously delivered courses with this configuration have worked correctly. However, one specific course is not being marked as complete.

In this course, we added three quizzes (each with about three questions). As per the client’s request:

• Each question allows only a single attempt.
• After clicking “Submit” for each question, the learner is shown the correct answer.

Please note that other courses also include quizzes built using the same template and settings, and those courses are marked as complete without any issues.

When we tested this course in SCORM Cloud, under the Compatibility settings, the “Completion Status of failed Success Status” is showing as “Unknown.”

Could you please help us understand what might be causing this issue?