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I understand that you have activated the Microsoft Entra ID P2 trial, created an app registration in the Microsoft Entra ID/Azure portal, and have now received an email to extend your license. Your requirement is to use the Microsoft Entra ID/Azure portal with a Client ID and Client Secret for authorization.
The Microsoft Entra ID P2 trial is valid for 30 days. Premium licenses are required to use features such as conditional access policies, Microsoft Entra ID Protection, and Microsoft Entra Application Proxy.
The app registration feature is available with the free-tier license. You can continue to use Microsoft Entra ID with your Client ID and Client Secret for authorization, and you do not need to purchase a specific plan for this.
To learn more about the features supported based on licenses: Microsoft Entra Licensing.
To keep accounts secure, Microsoft has enabled security defaults by default. Both new and existing tenants had a 14-day grace period to register for multi-factor authentication (MFA). You must register your MFA method within 14 days to protect your account. Please follow the prompts to complete your MFA registration.
For your reference: Security Defaults in Microsoft Entra
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Navya.
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