Hi,
Do you have at least one of the prerequisite certifications (Azure Administrator AZ-104 or Azure Developer AZ-204)? At least one of these is required in addition to passing AZ-400.
Please ask your question in the Microsoft Certification forum using link below. There are support moderators over there that will respond to your question in 1 business day and can assist with getting your certificate to show up:
https://trainingsupport.microsoft.com/en-us/newthread?threadtype=Questions&forum=mcp
Please click Accept Answer if above was helpful.
Thanks.
-TP