PBI reporting server-Maria DB-direct query

I'm tryng to do direct query to mariadb in PBI desktop and it just works fine.  However whenever i move the report to reporting server, it just doesnt work. 

following is the error I get when i try to run the report via browser - 

An unexpected error occurred
An unexpected error occurred. Please try again later.
Please try again later or contact support. If you contact support, please provide these details.
We couldn't connect to the Analysis Services server. Make sure you've entered the connection string correctly.: 
Request ID: bcac8abc-c1c8-e4be-63b3-f9ad8349d434
Time: Wed Jan 05 2022 12:39:24 GMT-0500 (Eastern Standard Time)
Service version: /powerbi/libs

I looked at different error logs and ng is what i could see - 

1. message in RSPortal.  Error message shown here has something to do with access. However the user mentioned is my id in the desktop where i created this PBI report. Why would reporting server complain saying my personal account (US\AF12345) has some access issues; whereas reporting server is supposed to run under PBIRS service account.. Am I missing somehting here?

2022-01-05 12:39:24.2109|ERROR|135|library|Throwing Microsoft.ReportingServices.Diagnostics.Utilities.WindowsAuthz5ApiException: , Microsoft.ReportingServices.Diagnostics.Utilities.WindowsAuthz5ApiException: Windows returned a ERROR_ACCESS_DENIED error when Reporting Services attempted to call the Windows Authz APIs. If this issue persists the Reporting Services account may not possess permission to perform authentication checks. Check the Windows Authz documentation for more information and details on diagnosing issues. Authz method: AuthzInitializeContextFromSid, Error code: 5, UserName: US\AF12345;| RequestID = bcac8abc-c1c8-e4be-63b3-f9ad8349d434 ClientSessionID = a6bb8265-4c27-15d1-0a04-0d3fba5247f8 
2022-01-05 12:39:24.2109|INFO|135|library|Unable to authenticate US\AF12345 by alias. The Windows domain controller may be unavailable - attempting to authenticate using UserToken.| RequestID = bcac8abc-c1c8-e4be-63b3-f9ad8349d434 ClientSessionID = a6bb8265-4c27-15d1-0a04-0d3fba5247f8 

2. ASManaged root log - it says datasource is unknown!!

2022-01-05 11:47:11.7300|INFO|66|GetV3ConnectionString Called - Engine connection string: Provider=Microsoft.PowerBI.OleDb;Mashup=UEsDBBQAAgAIAORdJVQ+Tv++xwAAACMBAAATABwARm9ybXVsYXMvU2bUCkAAAA6QAAABMAAAAAAAAAAAAAAAAA/QEAAFtDb250ZW50X1R5cGVzXS54bWxQSwUGAAAAAAMAAwDCAAAA7gIAAAAA; User principal name: [email protected]; dataSourceIds: {"protocol":"x-datasource","address":{"kind":"UnknownFunction","path":"UnknownFunction"}}; Root activity ID: e114d109-6fca-433a-9c75-64ac9a8d2b54.
2022-01-05 11:47:11.7300|ERROR|66|GetV3ConnectionString - Exception occured while retrieving credentials for data model connection string.System.NotSupportedException: The given data source kind is not supported. Data source kind: UnknownFunction.
   at Microsoft.Data.Mashup.DataSourceReference..ctor(String json)
   at Microsoft.PowerBI.ReportServer.ASEngineManagedRoot.PBIRSConnectionDetailsProvider.GetPathFromDSR(String dsrJson)
   at System.Linq.Enumerable.<>c__DisplayClass7_0`3.<CombineSelectors>b__0(TSource x)
   at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
   at System.Linq.Enumerable.<SelectManyIterator>d__17`2.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Microsoft.PowerBI.ReportServer.ASEngineManagedRoot.PBIRSConnectionDetailsProvider.GetDatasources(String userPrincipalName, String[] datasourceIds, Guid rootActivityId)
   at Microsoft.PowerBI.ReportServer.ASEngineManagedRoot.PBIRSConnectionDetailsProvider.GetV3ConnectionString(Guid rootActivityId, String userPrincipalName, String engineConnectionString, String[] datasourceIds, String contextualIdentity, String contextualIdentityKey, Boolean isDirectQueryExecution, PBIDedicatedProviderType& providerType, String& connectionString)

I'm really stuck and appreciate if ayonbe could help me here..