I am having this issue from last few days and no idea where it's going wrong. I have refresh schedule for the the report and getting this error each time.
Failure details: The last refresh attempt failed because of an internal service error. This is usually a transient issue. If you try again later and still see this message, contact support.
Column 'brandCampaign' in Table 'gentella_emailresponsesummary' contains a duplicate value 'E-Star_20180601_0819_es_fi_ac_170809' and this is not allowed for columns on the one side of a many-to-one relationship or for columns that are used as the primary key of a table. Table: gentella_emailresponsesummary.
I checked the table and there is no duplicate in that table. Even when I am refreshing the file from desktop it's not showing this error and refresh done successfully.