Hi,
Agreed, that NetExam is not much convenient for retaking exams.
If you didn't buy the exam and want to recertify, I think we had to put a purchase order to Extreme for TR-EXAM-1. Once they process it internally you will see on the top right corner that you have a voucher so if you go to the exam object you should be able to use it after clicking 'Add to cart'. But with retaking an already passed exam AFAIR we also had to write on behalf of students to Learn that 'there was a purchase with this and that purchase order #, so please activate Access Wireless exam for me as this platform doesn't allow me to do it by myself'. We did that couple of times. The exam will be either in your main dashboard in exams or you will still have to go to it through Transcript section.
Hope that helps,
Tomasz