Error in data transfer; details in application log

What causes this issue?

Errors occurred while copying to APO

System Response

Parts of the data cannot be posted.

How to fix this error?

For more details about the cause of the problem, see the application
log in the application log object CIF.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.