Quantity Conversion Interface: Func. Module Subroutine & not responding

What causes this issue?

The subroutine name in Table OIB04 is spelled incorrectly, or the system
being called is not responding in the time allowed.

System Response

This is an error and the system cannot proceed.

How to fix this error?

Check the spelling of the path and module name in Table OIB04 (Trans.
O588). If the spelling is correct, then contact your system
administrator. Try the same transaction and the same system functions
again. If that fails, it could be that a "time-out" is the problem.

Error message extract from SAP system. Copyright SAP SE.