So a couple of flights later I can see in my log file that I'm getting errors (for several of the new voices I added):
"Voice Load Error. Attempt to use voice Susan failed. Please set the Center voice to a different one.
System.ArgumentException: Cannot set voice. No matching voice is installed or the voice was disabled.
at System.Speech.Synthesis.SpeechSynthesizer.SelectVoice(String name)
at P2A_2020.modTTSGlobal.PlayATCPhrase(String Phrase, Boolean Publish, Boolean PlayBkgnd, String SugResp, EventHandler`1 SpeakCompleteEventHandler)"
Does anybody know how I can remedy this little problem?