Why do I have a message about duplicated values in empty table

you have a relationship between two tables in Power BI, and one of the columns in the table on the one side of the relationship has duplicate values. This is causing an error because many-to-one relationships require that the column on the one side has unique values.

To resolve this issue, you will need to identify the duplicate values in the column and either remove them or merge them into a single row. You can do this by using the "Remove Duplicates" or "Merge Queries" features in Power BI.

Once you have resolved the duplicate values, you should be able to establish the many-to-one relationship between the tables.