Refresh/authentication failes when combine .csv data from O365 group in report

I have a list of .csv log files archived in O365 Group Folder.

I'm able to import all data using PowerBI desktop. When publishing the report to the group Workspace the datasource shows an error that the credentials are not valid. When I re-enter the credentials the process is stuck and nothing happens.

I used following steps: https://powerbi.microsoft.com/en-us/blog/combining-excel-files-hosted-on-a-sharepoint-folder/