Ionic 4: SpeechRecognition startListening is not working in iOS

I am using Ionic speechRecognition plugin in Ionic 4 app. It is working fine in Android but it is giving below error in iOS when I call SpeechRecognition startListening method.

Error Domain=kAFAssistantErrorDomain Code=203 “Retry” UserInfo={NSLocalizedDescription=Retry, NSUnderlyingError=0x600003948cf0 {Error Domain=SiriSpeechErrorDomain Code=1 “(null)”}}

Can anyone please suggest me how can I solve this error in iOS ?