SSRS report subscriptions cannot be created

What the error does not make clear is, in order to be able to subscribe to a report not only must the data source be set to "Credentials stored securely in the report server" you must also not select the option "Impersonate the authenticated user after a connection has been made to the data source".

The way I did was to create a new data source in the report builder and explicitly provided the username and password there to be used. Then, used that username password with the new data source with the report and voila it worked.

The problem sounds like the report expects the user to provide credentials when it is viewed. When you create a subscription, it does not have the credentials to execute the report.

Go to the report, click the properties tab, then choose Data Sources in the left pane.

Are you using a shared data source? Is it using Windows integrated security? If so, can you change it to use a service account made just to run these reports? You may need to view these properties by viewing the data source itself.

If it is a custom data source is the option "Credentials supplied by the user running the report" selected? If so, can you change it to "Credentials stored securely in the report server"?

Either way, if you want to set up a subscription, I have made it work by providing credentials in the data source rather than have the user input them.

If you are worried about security, I would suggest managing that on the report level rather than the data source level.