hi ,initialize delta process error

I got error message in the monitor as following:

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Error when sending data request

Diagnosis

The request IDoc could not be sent to the source system using RFC.

System response

There is an IDoc in the Warehouse outbox that did not arrive in the ALE inbox of the source system.

Further analysis:

Check the TRFC log.

You can get to this log using the wizard or the menu path "Environment -> Transact. RFC -> In Data Warehouse".

Removing errors:

Check especially the authorizations for the background user in the SAP BW.

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how can i solve it ?