Authentication failure between Power BI Report Server and Sharepoint On-Prem

Hello, All

I operate both Sharepoint on-premise and Power BI Report Server which is installed upon a virtualized Windows Server 2016.

A problem is here that after inputting "connection strings" and "credentials" into Data Source and pushing Connection Test button, it's failed PBRS to connect to the sharepoint. Thing weird is it doesn't happen between the sharepoint and PBRS that is operated upon on Windows 10.