I have an SSIS package with a SQL Connection using the SqlClient Data Provider. Its connection string is set from a variable via an expression.

I have a .NET 4.8 Windows Service hosted on the SSIS server. It runs the SSIS package using the following process:

1. Call [catalog].[create_execution]
2. Call [catalog].[set_execution_property_override_value] to set the connection string variable
3. Call [catalog].[start_execution]

That all works fine.

Now I want to replace that Windows Service with a .NET 8 web service hosted in IIS on a different server.

• Its application pool account is the same as that used by the Windows Service. I have confirmed this using SQL Profiler.
• It uses the same 3 steps listed above to start the package.

The package starts, but fails with error:

Failed to acquire connection “MyConnection”. Connection may not be configured correctly or you may not have the right permissions on this connection.

Why?