Please download below Windows PC utility to debug your issue.
Debug version for rings once issue.
The "hook detection speed" is double (default is 200ms: label at 100ms)
1. click "Debug Trace" to enable the trace.
2. Begin to make the call with connected analog phone (start an incoming call to ring your analog phone).
3. After the call is connected or it failed to make the call, click on "OK" on the pop-up Window to stop the debug trace.
The trace file "Cell2Jack.trace" will be on the same directory as the application.