System &1 unknown in Transport Management System

What causes this issue?

An error occurred in the TMS communication layer.
System: <LS>&V2&</>
Function: <LS>&V3&</>
Error: <LS>&V4&</>

System Response

The function terminates.

How to fix this error?

Log this system on to the Transport Management System.
If this error occurs in the function TMS_CI_CHECK_ACCESSTOKEN, then the
TMS configuration was deleted in the SAP system <LS>&V2&</>.
Configure the TMS in this SAP system again.

Error message extract from SAP system. Copyright SAP SE.