@Ahsan Shakeel Thank you for reaching to us. As I understand you are trying to activate P1/P2 license in Azure AD B2C.
Azure AD B2C tenants don't use Azure AD Premium P1 or Azure AD Premium P2 licensing. Azure AD B2C uses Azure AD B2C Premium P1 or P2 licenses, which are different from Azure AD Premium P1 or P2 licenses for a Standard Azure AD tenant. Azure AD B2C tenants natively support some features that are similar to Azure AD Premium features
Refer to this article https://learn.microsoft.com/en-us/azure/active-directory-b2c/billing#change-your-azure-ad-pricing-tier:~:text=Change%20your%20Azure%20AD%20pricing%20tier it has the steps on selecting the pricing tier for Azure AD B2C
Reference: Billing model for Azure Active Directory B2C
Let me know if you have any further questions.
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