New Quizzes have a lot of quirks that need to be ironed out. One of which is the regrade option. As is, if you need to regrade a whole class, you'd need to do so manually for each student. The process is also time consuming. Here are the directions I received from Canvas Support for this issue: 

"To do this you will go into the quiz, and then click on the moderate tab. Then for each student, you
will click on their attempt. then click into the score area for one of the questions, and then click out, and then click the update scores at the bottom. This will pass the updated grade to the gradebook for
that student."

Helpful, but way too much time. We need a simple button that allows for regrading options, whether full class full quiz, full class single questions, or something else.