Problem with Scheduled Refresh on PowerBI Report Server

Hello,

I'm trying to create a scheduled refresh plan in PowerBI Report Server using:

• PowerBI Desktop optimized for Report Server (September 2019)
• PowerBI Report Server (September 2019)

To test this, I've created a Test directory, to which I have full permissions. The same user has System Administrator and System User permissions in the Site Settings.

When I test the connection it seems ok. but when I try to set up a shceduled refresh it give me an error:

An error has occurred. Something went wrong. Please try again later.

I have checked in the log folder (C:\Program Files\Microsoft Power BI Report Server\PBIRS\LogFiles), but I don't know which log files to check, there a lof of types: 

ReportingServicesService_XXX

ReportingServicesWMI_XXX

RSHostingService_XXX

RSManagement_XXX

RSOffice_XXX

RSPortal__XXX

RSPowerBI_XXX

I use local CSV file for the test, located in C:\ and shared as i read that it should be, so it can be accessed from \\servername\folder\test.csv

When I test the connection to the file - it is ok:

And here is the error when try to set up the Scheduled Refresh:

I can give you log file, but please tell me which one to copy.

Please help me with this issue.

BR