Hi @SIRAJUL ISLAM ,
The free certification exam is available for redemption starting April 7, 2021 and is valid until June 30, 2021. If you do not schedule and take your eligible exam within that timeframe, you will not be able to redeem your offer.
For more information, please see:
Microsoft Ignite Cloud Skills Challenge 2021: Free Certification Exam
https://learn.microsoft.com/en-us/learn/certifications/microsoft-ignite-free-certification-exam-offer-march-2021
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Best regards,
Leon