Start a conversation programatically stopped working

Hello Dear Intercom-Support-Team, 
as of recently we noticed a strange behavior in our application and it is no longer possible to start a conversation programmatically from our application. The server returns 400 http error on request.

We have not changed anything in the intercom settings (I have asked the entire support team) SDK Keys are not expired or so, and have been never changed. Other functions of Intercom Messenger are not affected.

Could You please help here, as we use this functionality to provide our customers the possibility to send us Device Logs.

Mobile Platforms affected: iOS, Android (both native Apps)

Intercom SDK Version: 15.5.0 (also tested with 15.6.2 the same behaviour)
 

POST https://jabaugui-android.mobile-messenger.intercom.com/messenger/mobile/conversations
Request:
{
  "body" : "App: lexoffice Android, Version 267 ….",
  "from" : {
    "id" : "{id here}",
    "type" : "user"
  },
  "app_id" : "{app id here}",
  "hmac" : "{hmac string here}",
  "user" : {
    "email" : "{my email here}",
    "type" : "user",
    "user_id" : "{user id here}"
  }
}

Response:
 

400 POST https://jabaugui-android.mobile-messenger.intercom.com/messenger/mobile/conversations

cache-control:no-cache
content-encoding:gzip
content-type:application/json; charset=utf-8
date:Fri, 16 Feb 2024 12:22:19 GMT
server:nginx
status:400 Bad Request
strict-transport-security:max-age=31536000
vary:Accept,Accept-Encoding
x-intercom-version:ae8c66d841ff238ea75264a694cb18faa958b982
x-request-id:0000dl33g36r9ir9u7kg
x-request-queueing:0
x-runtime:0.068291

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