3640892 - Group Reporting: Error pop-up in Data Monitor. System has been upgraded from release S/4HANA 1909.

User observes the following error pop-up right after an upgrade from release S/4HANA 1909 upon starting Data Monitor app:

Incorrect master data is found.
Warning: Incorrect assignments of consolidation groups to ledgers are found in your master data.
As described in SAP Notes 2868331, 2693872, and 2841647 you can't assign
different ledgers to consolidation groups within one version.
You can't continue to work with inconsistent master data. Therefore, you
need to open an incident for component FIN-CS-COR to correct your master data.

...

Due to the latest upgrade, no ledger could be assigned to this version.
The master data is incorrect and therefore you can’t use this version.
Please contact SAP to solve this issue.

...

The error may look differently regarding the listed versions.

The error may refer to incorrect master or transaction data, or both.

SAP S/4HANA Cloud Private Edition, SAP S/4HANA Finance for Group Reporting

KBA , FIN-CS-COR , S/4HANA Financial Consolidation, Core Processing , Problem