On some systems during the upgrade, the customized call flows are not migrated (the voicemail service .MDB file). However, the original call flows are still present in the editable file used by the Voicemail Pro client (the .VMP file).
Resolution
1.Connect to the voicemail service using the Voicemail Pro client.
2.Check that the customized call flows are shown.
3.Click Save & Make live.