There are 2 distinctive roles based access control in Azure (Azure RBAC & Azure AD RBAC). Azure RBAC is being used granting you the owner permission in a subscription.
Please check what is the value on following setting in Azure portal:
Navigate to Azure Active Directory > In the left pane, select Users > User settings > App registrations
If set Yes : - User can register application
If set No : - Although your account is assigned the User role, but the app registration setting is limited to admin users. Please ask your Azure AD administrator to either assign you one of the Azure AD administrator roles that can create and manage all aspects of app registrations.
In short - Your account needs to be part one of the Azure AD role to register the applications. Different Azure AD roles are available and you can pick the one closest to your requirment. AAD Roles are outlined here
For more reference : https://learn.microsoft.com/en-us/azure/active-directory/develop/howto-create-service-principal-portal#check-azure-ad-permissions
Best regards,