Instead of "Connected", call has status &1: Action not possible

What causes this issue?

In order to execute the requested function, an action on a call that
has just been connected must be executed. However, this call has the
status &V1&
Further information on the external software component:
&V3&
The server concerned is &V1&.

System Response

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

How to fix this error?

Procedure for System Administrators

The error can occur in 2 different places:
1. In the connected gateway
2. In the underlying CTI software
In this case the error occurred in (&V4&).
The return code for the underlying CTI software is: &V2&

Error message extract from SAP system. Copyright SAP SE.