Every student got the same question wrong
The question probably has no answer that can be graded correct. Open the quiz in the course builder and look for No correct answer on the question’s row. Open it, and the notice says why. Mark or fill in the right answer. Answers already given aren’t re-marked. See When the builder says a question has no correct answer.
A student’s attempt is marked Expired
They started a timed quiz and came back after its time ran out. The attempt stays as it was, doesn’t count toward the attempt limit, and the student starts a new one with the full time.
A student used up their attempts and needs another try
Press Reset attempts beside the quiz on the student’s page under Students. Their earlier attempts and answers stay in Reports, marked Reset. See Reset a student’s quiz attempts.
The builder says “Two answers have the same text”
A student who picks either answer gets the same result, because a pick is judged by its text. Change one of them.
A true/false question shows neither True nor False selected
Nothing is marked correct, so every student is being marked wrong. Pick one.
A brand-new question warns that a blank answer is marked correct
Expected. A new multiple-choice question starts with its first, still-empty answer marked correct, and blank answers aren’t saved. Type the answers and the notice goes away.
A short answer marked wrong looks right to me
It has to match one of your accepted answers exactly, apart from capitals and spaces at the ends. Add the spelling the student used as another line. See Short answer questions.
A question I deleted still shows in Reports, marked Archived
Working as intended. A question students have answered is kept with its answers so your records stay complete. It’s gone from the quiz and never served again.