AWS Java NoSuchMethodError using IVONA Text to Speech

I have started using IVONA TTS and AWS is a dependancy of it, so I have also imported that to the project. My problem is that when running even the sample Java application I get the following error:

Exception in thread "main" java.lang.NoSuchMethodError: com.amazonaws.auth.AWS4Signer.presignRequest(Lcom/amazonaws/Request;Lcom/amazonaws/auth/AWSCredentials;Ljava/util/Date;)V
    at com.ivona.services.tts.IvonaSpeechCloudClient.prepareRequest(IvonaSpeechCloudClient.java:292)
    at com.ivona.services.tts.IvonaSpeechCloudClient.prepareRequestForGetUrl(IvonaSpeechCloudClient.java:270)
    at com.ivona.services.tts.IvonaSpeechCloudClient.getCreateSpeechUrl(IvonaSpeechCloudClient.java:159)
    at filetest.TextToSpeech.main(TextToSpeech.java:49)

TextToSpeech.java:49 being:

System.out.println("Requested URL: " + speechCloud.getCreateSpeechUrl(createSpeechRequest));

I'm using AWS version 1.10.12 (latest), but I've also tried several other previous versions only to get the same error. I've checked the class file "AWS4Signer", and the method "presignRequest" does exist, so I'm confused as to why I'm getting this error. If needed, here is the sample I used.

I'll be happy to add any more information if required. Any help would be greatly appreciated.