Failed to get HTTP platform singleton instance. Error: 27, C#/Unity 6.1, SDK v1.44, Ubuntu 25.04

[pholz]

My Unity project has a SpeechRecognizer which successfully produces Recognizing and Recognized events and everything works fine when run on MacOS. However, when I build for Linux (ubuntu 25.04 x86_64) and deploy and run it on the Linux machine, I get the error in the title. I have seen the related issues, but they were reported to be solved in the latest release, which does not seem to be the case. Another related issue suggests downgrading the SDK, but this is not possible for Unity as far as I can see, because there is only a single link to a Unity package in the samples repository, and it points to 1.44.

Unity Error Log:

Recognition canceled: Error
UnityEngine.Debug:ExtractStackTraceNoAlloc (byte*,int,string)
UnityEngine.StackTraceUtility:ExtractStackTrace () (at /home/bokken/build/output/unity/unity/Runtime/Export/Scripting/StackTrace.cs:37)
UnityEngine.DebugLogHandler:Internal_Log (UnityEngine.LogType,UnityEngine.LogOption,string,UnityEngine.Object)
UnityEngine.DebugLogHandler:LogFormat (UnityEngine.LogType,UnityEngine.Object,string,object[])
UnityEngine.Logger:Log (UnityEngine.LogType,object)
UnityEngine.Debug:Log (object)
AzureSpeechRecognition:OnCanceled (object,Microsoft.CognitiveServices.Speech.SpeechRecognitionCanceledEventArgs) (at /Users/peterho/code/corax/corax-fe-front/Assets/Scripts/azure_speech_unity.cs:368)
Microsoft.CognitiveServices.Speech.SpeechRecognizer:FireEvent_Canceled (intptr,intptr,intptr)

(Filename: /Users/peterho/code/corax/corax-fe-front/Assets/Scripts/azure_speech_unity.cs Line: 368)

Recognition error: ConnectionFailure - Failed to get HTTP platform singleton instance. Error: 27 SessionId: 38f4a886802645b59fd669434e323f4c
UnityEngine.Debug:ExtractStackTraceNoAlloc (byte*,int,string)
UnityEngine.StackTraceUtility:ExtractStackTrace () (at /home/bokken/build/output/unity/unity/Runtime/Export/Scripting/StackTrace.cs:37)
UnityEngine.DebugLogHandler:Internal_Log (UnityEngine.LogType,UnityEngine.LogOption,string,UnityEngine.Object)
UnityEngine.DebugLogHandler:LogFormat (UnityEngine.LogType,UnityEngine.Object,string,object[])
UnityEngine.Logger:Log (UnityEngine.LogType,object)
UnityEngine.Debug:LogError (object)
AzureSpeechRecognition:OnCanceled (object,Microsoft.CognitiveServices.Speech.SpeechRecognitionCanceledEventArgs) (at /Users/peterho/code/corax/corax-fe-front/Assets/Scripts/azure_speech_unity.cs:372)
Microsoft.CognitiveServices.Speech.SpeechRecognizer:FireEvent_Canceled (intptr,intptr,intptr)

[pholz]

Given the formal requirements, I also tried it on Ubuntu 24.04 LTS now, and I am getting the same error.

[pholz]

Managed the following workaround:

• Use ubuntu 24.04 LTS
• Do not use the Unity asset package (remove it from the project), but install the Speech SDK via Unity's NuGet, and select version 1.37 of the SDK
• Install openssl 1.1 from Focal (20.04 LTS) channel

This is super ugly but it seems to work equally well in terms of the speech API. I'd rather not close this issue because I think it needs to be solved - otherwise I can never upgrade the SDK.

[pholz]

unfortunately this breaks the whole thing on macOS because the NuGet package doesn't properly glue things together there. Please fix.

[github-actions]

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