Sql-server – Cannot process cube using SQL agent job in SSMS

I have an issue where we have a user who has used his own AD account to create and deploy the cube back when he was the sole DBA.

I would like to have an proxy account with a password known internally instead of his own credentials.

For this I have created a new AD account, ProcessCube, which I have given sysadmin rights on the underlying SQL Engine. I have also created a role called Process cube on the SSAS database with read and write rights on every cube and read rights on data sources.

In SSAS I have double clicked the data sources and under Impersonation mode I have replaced the old credentials with the credentials of the newly created AD account ProcessCube.

I have not deployed the cube with the new credentials, but rather let the SQL SSAS command in the SQL agent do the trick, do I need to deploy the cube first?

In the SQL Agent I've made ProcessCube the Owner of the job which is a SQL Server Analysis Server Command.

When I try to execute the SQL agent job I get the error:

The following system error occurred:  The user name or password is incorrect.  Source="Microsoft SQL Server 2016 Analysis Service

I assume I need some more credentials, what more do I need? What have I missed?

The command I try to execute in the agent is as follows:

<Batch xmlns="http://schemas.microsoft.com/analysisservices/2003/engine">
  <ErrorConfiguration xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ddl2="http://schemas.microsoft.com/analysisservices/2003/engine/2" xmlns:ddl2_2="http://schemas.microsoft.com/analysisservices/2003/engine/2/2" xmlns:ddl100_100="http://schemas.microsoft.com/analysisservices/2008/engine/100/100" xmlns:ddl200="http://schemas.microsoft.com/analysisservices/2010/engine/200" xmlns:ddl200_200="http://schemas.microsoft.com/analysisservices/2010/engine/200/200" xmlns:ddl300="http://schemas.microsoft.com/analysisservices/2011/engine/300" xmlns:ddl300_300="http://schemas.microsoft.com/analysisservices/2011/engine/300/300" xmlns:ddl400="http://schemas.microsoft.com/analysisservices/2012/engine/400" xmlns:ddl400_400="http://schemas.microsoft.com/analysisservices/2012/engine/400/400">
    <KeyErrorLimit>-1</KeyErrorLimit>
    <KeyNotFound>IgnoreError</KeyNotFound>
    <NullKeyNotAllowed>IgnoreError</NullKeyNotAllowed>
  </ErrorConfiguration>
  <Parallel>
    <Process xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ddl2="http://schemas.microsoft.com/analysisservices/2003/engine/2" xmlns:ddl2_2="http://schemas.microsoft.com/analysisservices/2003/engine/2/2" xmlns:ddl100_100="http://schemas.microsoft.com/analysisservices/2008/engine/100/100" xmlns:ddl200="http://schemas.microsoft.com/analysisservices/2010/engine/200" xmlns:ddl200_200="http://schemas.microsoft.com/analysisservices/2010/engine/200/200" xmlns:ddl300="http://schemas.microsoft.com/analysisservices/2011/engine/300" xmlns:ddl300_300="http://schemas.microsoft.com/analysisservices/2011/engine/300/300" xmlns:ddl400="http://schemas.microsoft.com/analysisservices/2012/engine/400" xmlns:ddl400_400="http://schemas.microsoft.com/analysisservices/2012/engine/400/400">
      <Object>
        <DatabaseID>DataBaseID</DatabaseID>
      </Object>
      <Type>ProcessFull</Type>
      <WriteBackTableCreation>UseExisting</WriteBackTableCreation>
    </Process>
  </Parallel>
</Batch>