Like a lot of people I also have trouble with TTS on Lollipop.
I have both Primo and Nextgen installed. When I had KitKat on my phone both worked fine with TTS engines (nuance and loquendo). Now that I have upgraded to Lollipop Primo still works fine with all TTS engines while NextGen refuses to work with any of them. No TTS voices appear as possible selections in the application no matter what TTS engine I'm using.
I have downloaded several english TTS voices from here but none of them work on my phone. There's something strange going on with NextGen as everything worked fine on KitKat.