To add any new accounts to Azure AD you need to have appropriate roles assigned to user who signs in to Azure portal.
If you are a normal user in the Azure AD then you will not have permissions to add any new user.
This task can be performed by Global administrator.
To know Global administrator of your tenant you can follow below steps,
• Open Windows PowerShell as administrator.
• Run command “Install-Module azuread”
• Once installed you can run command “Connect-AzureAD” and enter user credentials once it asks for.
• Once you login, you can run command “Get-AzureADDirectoryRole”.
• From the output you can copy the object ID of Global administrator
• Run command “Get-AzureADDirectoryRoleMember -ObjectId "Paste the object ID of global admin that was copied earlier"
• You will get the list of users with global admin role assigned.
Now you can contact any global admin from the list and ask them to assign an admin role to you. Or you can ask global admin to add a new account that you were trying to add in Azure AD.
Do let me know if you have any further questions.
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