I filed a bug: http://bugs.pearsoncomputing.net/show_bug.cgi?id=2657
I can't get KTTSMgr to find any voices on two different installations on Stretch or two different installations on openSUSE 42.1. If it works for you, please tell me what you're running it on, and if you can, what I might be overlooking WRT to setup to make it work.