Can't Display the Visual

Have you checked your datasource credentials?  If your data source is a SQL server follow the below steps.

Go to the folder where your PowerBI report/dash is located in Report Server.  Click the 3 dots to the right of the report's name.  On the pop out window, click 'Manage'.   Now on left panel click Datasource.

Under the Credentials section:

If you are using a SQL account make sure it is set to Basic Authentication, the credentials are correct, and test the connection.  

If you are using AD, choose Windows Authentication, verify the credentials are correct, and test the connection.  

Regardless if you are using a SQL account or AD account, make sure the account has READ access to the tables/views in SQL Server.