If you fail the exam, you will retake it. It will only make you lose credit for this course. If you graduate with enough credits, you will definitely get it. Diploma.
But some units will care about this. So when applying for a job, try to avoid mentioning this.
As long as the other aspects are good enough. For example, if there are other certificates with high gold content, they will. . . . .
Hehe, work hard by yourself.