3752598 - Warning message in GRDC Define Data Mapping App "The selected source instance is unavailable." and "Can't retrieve <source table> fields from the source instance "

• Intermittent warnings appear in the data mapping app when opening or editing a source definition; messages later change and disappear, and the mapping can then be completed.
• Error: "The selected source instance is unavailable. You can still create a definition, but it does not include instance-specific custom fields. The legacy journal entry API will be used, which may not retrieve all data required for consolidation.

There may be different causes outlined containing the table to read, the BTP destination used and the odata service used to read depending on the BTP service destination. For example the error message can be 

1. Can't retrieve ACDOCU fields from the source instance S4HanaCConsoEndpoint using service API_GRTRANSACTIONDATA_SRV. Error: HTTP 401 - Unauthorized  or

2. Can't retrieve ACDOCA fields from the source instance S4HanaCConsoEndpoint using service API_GLACCOUNTLINEITEM. Error: HTTP 403 - Forbidden

SAP Group Reporting Data Collection connected to S/4HANA Private Cloud Edition

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