Power Bi Service SharePoint Schedule refresh not working

On a different project, I use Power BI + SQL Server + Gateway.

• This seems to work seamlessly, updating dataset via auto-refresh is great.

In this project I am working now, the back-end is SharePoint lists from a SharePoint Site.

• I set the Scheduled Refresh to ON
• Refresh frequency to DAILY
• Timezone 
• Time (8 different times of day)

Prior to the above, I have also set the Data source credentials (Edit credentials) to 

• sharePointSiteUrl: https://this-is-the.sharepoint.com/sites/mySite
• Authentication method: OAuth2
• Privacy level setting for this data souce: Organizational

PROBLEMATIC OUTPUT:

• Before, it somewhat reverts to some previous data, thus, not updating but back-dating.
• Now, the data shows BLANK. when auto-refreshed or manually clicked on
  • Workspace -> Datasets -> Actions -> Refresh Now

The client wants it at least updating even without Power BI Desktop intervention.

Am I doing something wrong about SharePoint and Power BI connectivity? Please comment down if you had this experience.