i am having the same issue in ios 13. I got the following error,
2020-01-21 15:30:41.549170+0530 Pro@Me[2212:613705] [Utility] +[AFAggregator logDictationFailedWithError:] Error Domain=kAFAssistantErrorDomain Code=1700 "(null)"
2020-01-21 15:30:41.553271+0530 Pro@Me[2212:613445] [aurioc] AURemoteIO.cpp:1590:Start: AUIOClient_StartIO failed (561145187)
2020-01-21 15:30:41.553429+0530 Pro@Me[2212:613445] [avae] AVAEInternal.h:109 [AVAudioEngineGraph.mm:1544:Start: (err = PerformCommand(*ioNode, kAUStartIO, NULL, 0)): error 561145187
2020-01-21 15:30:41.556057+0530 Pro@Me[2212:613445] THREAD WARNING: ['SpeechRecognition'] took '42.260986' ms. Plugin should use a background thread.
2020-01-21 15:30:41.556959+0530 Pro@Me[2212:613445] startListening() recognitionTask error: Error Domain=kAFAssistantErrorDomain Code=1700 "(null)"