Cannot create a connection to data source error
I have setup SSRS with 3 data models using 3 different datasources on one server. I can create reports ok, but if any of the other users I want to access these reports tries to open the report I created or run there own reports (they can create a report), it gives them the error:
Report Execution Error
Cannot create a connection to the data source 'datasource1'
I do not recieve this error, but the other users do. I have set the other users as System administrator in the site-wide permissions, so they have access to everything.
Everything is set to integrated windows authentication.
On the Reporting Server Configuration Manager, the Unattended Execution Account is not selected and is blank.
What could cause these users not to be able to run existing or new reports they create?
Thanks for any help,