smart narrative summaries Issues

Hello, I wish to use smart narratives in Power BI. To do so, I've created dynamic values (updated with my data). When I use a table that's almost identical (cumulative up to June), the creation proceeds without issue. However, when I use the same table with a cumulative period up to December, the creation of dynamic values is erroneous with the error message: "This calculation does not return a unique value," or it indicates that the column does not exist in the table (which is not the case). The generated terms are also nonexistent (in Questions/Answers).

Could you help me please ?

Cynthia