Azure Cost Management - Editor de Power Query Expression.Error No se puede convertir el valor null

Hey Anonymous ,

That would be much apprepciated. I can't seem to wrap my head around why this error occures so sporadically. Even when I don't have any transformation steps there are occasions where the data query returns the same error. Other times - with the same data query and the same Power BI Desktop file - it works perfectly fine.

This is my blank query that sometimes works and sometimes doesn't. 

Below is how I connect to the Azure Cost Management tool. For privacy reasons, I have removed the enrollment number. In my query, I use the correct enrollment number, and input 1 for the number of months.

Thanks,

Giulio