Hi Suriya,
Do you already have Active Azure Administrator Associate (AZ-104) or Azure Developer Associate (AZ-204) certifications?
At least one of the above is required in addition to passing AZ-400 to earn DevOps Engineer Expert certification. If you don't have the pre-requisite certification yet then all you need to do is pass AZ-104 or AZ-204 exam and then your certificates will show up.
Please click Accept Answer if the above was helpful.
Thanks.
-TP