Test accessibility

I also am trying to set up my module to limit the number of times a student takes the test. I have one test with several test sections that are placed throughout the module, and I am using a custom results page that shows the overall score. I am not using an LMS and am publishing to CD.I tried this suggestion and for some reason it is not working for me. As far as I can tell, I have done it right, but it still allows me to change my answers after I go in a second time. Any ideas what I may be doing wrong?