First and foremost, download Gateway Install from Power BI Online website: https://app.powerbi.com.

> We need to set up email registered in Power BI website.

> On-premises data gateway window, let register a new gateway on this computer.

Note: If you have already installed Power BI Gateway, you can search On-premises data gateway in search window.

> There are some On-premises data gateway as below:

> Open Power BI Desktop, navigate to File > Options and settings > Data source settings.

Note: Note: Be assumption that we already connect successfully Amazon RDS postgres from Power BI Desktop and the issue relates to RDS certification has resolved.

> Change permission by Edit Permissions, no Encrypt connections to avoid SSL upon using power bi gateway.

> Move to Power BI app website, we will need to enter Data Gateway that generated from local machine. Enter Username and Password to connect.

An exception occurred: Please install Npgsql version 4.0.10.0 or earlier. (Session ID: 0b5711b9-635d-47ed-a93c-685c1d6a38c8, Region: us)

> How do you install Npgsql 4.0.10 WITH GAC? Click the link here to get Npgsql-4.0.11.msi. You need to setup “Entire feature will be installed on local hard drive" for Npgsql GAT installation.

> Open On-premises data gateway > Service Settings, you will need to Restart now and try again with website powerbi.