Hello @Neha Ghuraiya ,
Welcome to the Microsoft Q&A!
Most likely you are not able to create a new application and this option is greyed out for you as one of the main prerequisite doesn't complete:
"you must have one of the following roles: Global Administrator, Cloud Application Administrator, Application Administrator, or owner of the service principal."
You can confirm your current role assignments by simply going to the => Default Directory | Roles and administrators
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(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Sincerely,
Olga O