Data source information is not found in Power BI service

Question

I am currently trying to work through the following tutorial from Power BI:

https://learn.microsoft.com/en-us/analysis-services/tom/create-tables-partitions-and-columns-in-a-tabular-model?view=asallproducts-allversions

I did everything exactly as in the tutorial, except that I used a personal database from my SQL server. I am getting the following error:

{"error":{"code": "Premium_ASWL_Error", "pbi. error":{"code": "Premium_ASWL_Error", "parameters":{}, "details":[{"code": "Premium_ASWL_Error_Details_Label", "detail":{"type":1, "value": "An unexpected internal error happened while obtaining the credentials for the data source '<ccon>13</ccon>': data source information is not found in Power BI service."}}]}}

Upon further investigation, I notice that the error only occurs when the Column part is present during table creation. If I comment the column part, then the error does not occur (but then I also have no columns in my table):

dbWithDataSource.Model.Tables.Add(new Table() 
{ 
   Name = dbWithDataSource.Model.Tables.GetNewName("Individual Customers"),
   Description = "Individual customers (names and email addresses) that purchase Adventure Works Cycles products online.", 
   Partitions = { 
      new Microsoft.AnalysisServices.Tabular.Partition() { 
         Name = "All Customers", 
         Source = new QueryPartitionSource() { 
            DataSource = dbWithDataSource.Model.DataSources[dataSource],
            Query = @"SELECT [city], [street]
                      FROM [xyz].[building]"
         } 
      } 
   }, 
   Columns = 
   { 
      new DataColumn() { 
         Name = "Column1", 
         DataType = Microsoft.AnalysisServices.Tabular.DataType.String, 
         SourceColumn = "city", 
      }, 
      new DataColumn() { 
         Name = "Column2", 
         DataType = Microsoft.AnalysisServices.Tabular.DataType.String, 
         SourceColumn = "street", 
      }
   } 
});

Does anyone have an idea where my difficulties might be?

Maybe some more helpful information:

• I am using the PPU (Premium Per User) test license