Schedule Refresh failed after gateway connection testing

1) I have created PBI report which database server is the source , we have specific table in DB from where i'm getting the input 

2) Inorder to set up schedule refresh i have setup  gateway connection (with system account) and tried to test with some timeframe , when i checked at that timeframe , i got below error 

Here , my database name "Cycle_ID"(I have my table in it , from where i imported data into PBI ) but not "CycleDB", 

as we see in errror , it throws error on "i do not have access for "CycleDB" (though i don't use it ) 

"Last refresh failed: Mon Aug 31 2020 16:35:30 GMT-0400 (Eastern Daylight Time)
There was an error when processing the data in the dataset.Hide details
Data source error: {"error":{"code":"DM_GWPipeline_Gateway_MashupDataAccessError","pbi.error":{"code":"DM_GWPipeline_Gateway_MashupDataAccessError","parameters":{},"details":[{"code":"DM_ErrorDetailNameCode_UnderlyingErrorCode","detail":{"type":1,"value":"-2147467259"}},{"code":"DM_ErrorDetailNameCode_UnderlyingErrorMessage","detail":{"type":1,"value":"Microsoft SQL: The server principal \"system_account_name\" is not able to access the database \"CycleDB\" under the current security context."}},{"code":"DM_ErrorDetailNameCode_UnderlyingHResult","detail":{"type":1,"value":"-2147467259"}},{"code":"Microsoft.Data.Mashup.ValueError.Class","detail":{"type":1,"value":"14"}},{"code":"Microsoft.Data.Mashup.ValueError.DataSourceKind","detail":{"type":1,"value":"SQL"}},{"code":"Microsoft.Data.Mashup.ValueError.DataSourcePath","detail":{"type":1,"value":"<server_name>.com;Cycle_ID"}},{"code":"Microsoft.Data.Mashup.ValueError.Message","detail":{"type":1,"value":"The server principal \"system_account_name\" is not able to access the database \"CycleDB\" under the current security context."}},{"code":"Microsoft.Data.Mashup.ValueError.Number","detail":{"type":1,"value":"916"}},{"code":"Microsoft.Data.Mashup.ValueError.Reason","detail":{"type":1,"value":"DataSource.Error"}}],"exceptionCulprit":1}}} Table: BackupReviewerTSOID."

here my main question is , why it shows error that says, "The server principal \"system_account_name\" is not able to access the database \"CycleDB\" under the current security context."}},"  , though i don't use it in my report query ?