I know this is working fine since I just tested it a few days ago, but I think the issue you are seeing probably has something to do with replacing the references to Slt (which is a FliteController voice) with Beatrice (which is a NeatSpeech voice, so they aren’t really 100% interchangeable in terms of how they are initialized and which methods need to be used with them). It sounds a bit like you’re using the sample app, is that correct? Could you instead start from scratch and use the tutorial tool here:
selecting “Offline speech synthesis with better voices (paid plugin)” in order to build an app that is designed for use with NeatSpeech from the start? My other advice is to make sure that you’ve dragged in the folder VoiceData, which is something that sometimes gets overlooked in the instructions. Let me know if those steps help.