SAPphone &1: OLE error (&2 (0x&3))

What causes this issue?

The SAPphone TAPI client could not be found on the telephony server.
There are a number of possible causes:
The client is not installed
The registry entry refers to the wrong directory. The entry is called
'SAPphone TAPI Client' and must contain a parameter 'LocalServer' which
specifies the path name and program name for the SAPphone TAPI client.
(Example: LocalServer=c:\sapphone\sphtapic.exe)

System Response

Function canceled.

How to fix this error?

Please check whether the TAPI client is installed and if the registry
entry is correct.

Error message extract from SAP system. Copyright SAP SE.