In the Power BI service, go to the workspace that contains the dataset.

Click on the dataset and then on the settings.

Check the 'Data source credentials' and make sure they are configured correctly.

If the credentials are set, try updating them (re-enter the password) and test again.

If the dataset uses a live connection to an Azure Analysis Services model, then check the AAS model permissions.

If the dataset is imported (not live), then check the gateway and the data source permissions.

If the issue persists, consider changing the authentication method to one that is more universally accessible, such as OAuth2.

Also, check if the custom visual is using a direct query and if the user has the necessary permissions for the underlying data source...✨