Cant Access Bolt IOT & ML Cerification Exam

I have completed the course, created the hackster project and answered forum answers. Now I just have to give the exam but when i am entering the course exit code from in the coupon code section it is giving this error.
Please help asap

Maybe that time it has a technical shutdown, try again.
Also be sure that you haven’t started the exam before even by mistake as you can give certification test once with a coupon code.
If the issue still remains contact at with your details.
Hope it helps!!