Error: Cannot open server ‘xxx’ requested by the login. Client with IP address ‘xx.x.xxx.x’ is not allowed to access the server. To enable access, use the Azure Management Portal or run sp_set_firewall_rule on the master database to create a firewall rule for this IP address or address range. It may take up to five minutes for this change to take effect.

This is an error you get when you did not allow the client to access the server using the firewall, see the docs on how to do that.

Now, this

ADO.NET (Microsoft Entra integrated authentication)

Server=tcp:MyDBServer.database.windows.net,1433;Initial Catalog=MyDB;Persist Security Info=False;User ID=MyUID;MultipleActiveResultSets=False;Encrypt=True;TrustServerCertificate=False;Authentication=”Active Directory Integrated”;

Error: Cannot use ‘Authentication=Active Directory Integrated’ with ‘User ID’, ‘UID’, ‘Password’ or ‘PWD’ connection string keywords.

indicates that you should not supply an user id when using “Active Directory Integrated” authentication

If you want “Active Directory Integrated” authentication against your Azure Database you will need to switch to the Microsoft.Data.SqlClient namespace, see this blogpost. There is a guide on how to do that.

That also means you need to update to at least .Net Framework 4.6.2 as seen here

So, if you don’t want to, or can’t do use a connection string with username and password and make sure network access is allowed.

The default provider in Azure for connection strings should be System when you are working with them in a.NET Framework 4.5.2 application. SQL Server databases can be used using Data.SqlClient.

You indicated that you are utilizing Azure AD (previously known as Entra authentication), so it is imperative that you verify that the authentication techniques and connection string format are valid.

Measures to Recognise and Fix:

Examine the format of the connection string. Make sure Azure SQL Server has the connection string formatted appropriately. A small format difference exists between SQL authentication and Entra (Azure AD) authentication.

For Authentication

Data Source=<your_server>.database.windows.net;Initial Catalog=<your_database>;User ID=<your_username>;Password=<your_password>;

Example of Entra (Azure AD) Authentication: If your database connections are made with Entra authentication, then:

Data Source=<your_server>.database.windows.net;Initial Catalog=<your_database>;Authentication=Active Directory Integrated;

Alternatively, if you’re authenticating with a particular client ID (Service Principal):

Data Source=<your_server>.database.windows.net;Initial Catalog=<your_database>;Authentication=Active Directory Service Principal;User Id=<client_id>;Password=<client_secret>;