I am helping a teacher with a similar problem. A short quiz with 2 essay questions. The questions looked like a copy/paste job as there was surrounding html code around the instruction.
Students had tried it and their response text box didn't appear.
I tried it in student view and the box didn't appear.
I removed the extra html and it still didn't work in student view.
I reset student view, then it worked correctly.
Actual students still couldn't access.
I am in the process of asking students to clear cache/cookies and try again.
I'll update here when I get an answer, but fingers crossed.
*students are using random selection of laptop types and browsers.