Hello @Alam-3427 ,
Thanks for reaching out.
To use Azure AD Application Proxy, you must have an Azure AD Premium P1 or P2 license. For more information about licensing, see Azure Active Directory Pricing and you also try premium license by going to the Directory + subscription filter > select the correct Azure Active Directory tenant. Then go to Azure Active Directory > Licenses > Overview. In the top right under "Quick tasks" select "Get a free trial." Select Azure AD Premium P2 and select Activate.
Note: Enable Application Proxy button would be grayed out, when there's no Azure AD Premium P1 or P2 license and an Azure AD Application Proxy Connector installed so after you successfully activated premium license and install your first connector, the Azure AD Application Proxy service will be enabled automatically.
Hope this helps.
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