Need help for AWS Postgres connection issue from Power BI Service

Greetings,

I'm currently working on a project to use the Power BI Service to connect to an AWS Postgres database via Direct Query to build reports and dashboard out of it. The connection using Power BI Desktop is successful and I'm able to connect and refresh the model but with the Encrypt Connections unselected and Privacy Level set to Private in the Data Source Settings. Everything seems work in this way. However, there is some issue happens when I was updating the credential in Power BI Service. 

First, it prompts me to update the missing credential. So, I go to the Settings page to update my credential.

When I had done updating and going to submit it, an error shows. I understand that it might due to some permission issues but I need some further clarification. Have gone through quite a lot of posts but still doesn't find one that fully matched my issue.

I have tried also to update the credentials from the dataset settings which is shown in the image below but it doesn't work as well.

Looking forward to have an discussion and come out with a solution for my issue. Thanks and regards.

KeAn02