Error occured when creating link to HR System

What causes this issue?

During the clearing reset, you could not confirm the document data for
invoice document &V3& &V4& to HR (Third Party Remittance) since the
system could not create a connection to the HR system.

System Response

Since the HR system could not be reached, the confirmation of the
invoices as 'Not paid' was not possible. The system returns error
reason "&V1& &V2&".

How to fix this error?

The confirmation must be executed manually in HR.

Error message extract from SAP system. Copyright SAP SE.