This report contains dynamic datasources, which cannot be refreshed in Power BI Report Server.

Hi All,

When I want to schedule a new refresh plan I get the following error message from the report server: 

1056505856: This report contains dynamic datasources, which cannot be refreshed in Power BI Report Server.

My datasources consist only of excel files or folder paths to excel files en csv files, no other kind of datasources. 
Is it because of the csv files, which seem to be defined as dynamic datasources, or what do you guys think that could generate those error messages?

thank you!