Hi Sandra,
Participants who have completed a Microsoft Event after July 13, 2020 onwards are entitled for a voucherless discount by entering the registered email address on the Exam Discount page.
Just a heads up, our engineering team are aware of the issue in claiming the discount for Ignite Cloud Skills Challenge March 2021 and Virtual Training Days which has been resolved today. You may refer to this sticky post.
Meanwhile, learners who faced issue redeeming/claiming their discounts and register for an exam may try the steps below:
Sign-out from the browser
Clear cache and Delete cookies. Restart your browser session
Use an "InPrivate/Incognito" browser session or try on a different browser
Allow all third party cookies through the browser settings
If you are using a work computer, you may try personal machine to ensure that there will be no restriction
On the Exam Discount page, enter the email address registered in the event in all lower case letters and “Check for Eligibility”
You may also follow the steps from this link: Microsoft Ignite Cloud Skills Challenge 2021: Free Certification Exam
In the event that you are still unable to proceed, please provide us with a complete PSR (Problem Steps Recorder) showing the steps above until it shows no discount and attach it via private message so we can forward this to our Support team for investigation. Also include the confirmation email for completing the event.
You may refer on the image below to access private message:

I look forward to your response. Please note that if no response is received after two business days, the case will be closed and locked. After the case is locked, we will no longer be able to respond, even through Private Messages.
Regards,