If students report that they are unable to see their Quiz grade, this is often attributed to the quizzes Review Options. In order for a student to see their grade after completing a quiz or after the quiz has closed, 'Points' or sometimes 'Marks' need to be marked for the score to be visible:

Some additional definitions are below:

When Items can be Reviewed

Immediately after the attempt = This will show the students the marked items below regardless of other quiz settings.
Later, while the quiz is still open = This will show the students the marked items below after their attempt, but the grade will disappear once the quiz is closed.

After the quiz is closed = This will show the students the marked items after the quiz close date.

What Items can be Reviewed

The attempt = This will allow the student to review the questions that were on the quiz.

Whether correct = This will display whether the student got the answer for the question right. If it is wrong, they will see a red 'X' over their answer, but they will not be provided with the correct answer.

Points/Marks = This will allow the student to view the score they earned.
Specific feedback = This is feedback programmed into the question. I.e. if the student answers A, but the answer is C, it will give them a hint or say something like 'try again.'

General feedback = This is general feedback for the quiz, such as 'good job.'

Right answer = This will allow the student to review the quiz questions and it will show them the correct answer by putting a green check-mark to the left of the answer.

Overall feedback = This is the specific feedback that you provide to the student.

If you do not distinctly remember setting up feedback within your quiz questions, the feedback fields are likely irrelevant.