Internet explorer or Chrome should be fine, i hope. did you use firefox ah?
may i know if you took the exam from India or outside india?
I took it using Chrome and it was fine. If I remember correctly, there is no back button in the exam.
Confirm that you aren't running any extensions that could interfere with the exam site, just to be sure.
You get to take the exam three times, so try again!
@ChrisG is correct. There is no back button in the exam, nor can you mark questions for review later. I assume it is because it is already an open note exam.
Use the results emailed to you after completing the exam so you know what categories/areas to review again before you try again 🙂