There was a data source access error. Contact gateway administrator error on the report

Hi , Hemanth_PBIuser 

Based on your issue description and my research, actually the SSAS data source is a special data source which is different from other data sources published in the Power BI service, when using SSAS, each time a user interacts with a report connected to Analysis Services, the effective user name passes to the gateway and then passes on to your on-premises Analysis Services server. The email address that you use to sign in to Power BI passes to Analysis Services as the effective user in the EffectiveUserName connection property.

The email address must match a defined user principal name (UPN) within the local Active Directory (AD) domain. The UPN is a property of an AD account. The Windows account must be present in an Analysis Services role. If a match can't be found in AD, the sign-in isn't successful. To learn more about AD and user naming, see User naming attributes.

User Naming Attributes - Win32 apps | Microsoft Learn

And for this special data source, Power BI also design an easy for the "Mapping user name" for the gateway server when we try to use the AAD account signed in to be mapped to the defined user principal name (UPN) within the local Active Directory (AD) domain access the SSAS when using on-premise data gateway refresh data or query data:

You can configure custom UPN rules in Power BI for Analysis Services data sources. Custom rules help if your Power BI service sign-in name doesn't match your local directory UPN. For example, if you sign in to Power BI with [email protected] but your local directory UPN is [email protected], you can configure a mapping rule to pass [email protected] to Analysis Services.

For the steps description and detailed explanation, please refer to this official document:

Manage SQL Server Analysis Services data sources - Power BI | Microsoft Learn

Thank you for your time and sharing, and thank you for your support and understanding of PowerBI! 

Best Regards,

Aniya Zhang

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