"Subscriptions cannot be created because the credentials used to run the report are not stored, or if a linked report, the link is no longer valid" error

Get the aforementioned error. I have modified my Data Source many times trying different settings. I created a SQL Login called RS_Subscriber, local machine acct the same name, added the same as a user for our database and the ReportServer database. Tried with and without the Use as Windows credentials when connecting to the data source checked. I Test the connection okay but keep getting the #$^^$& error message.

Does anyone have explicit instructions on what type of account, where to create the account, what rights the account needs in order for the stored data source credentials to work?