Web widget sdk: black screen on Android

Hi
We just implemented the Web widget sdk into our ios and android apps.
Working well on iOS, however on Android I get a black screen when launching the messaging activity

Zendesk.instance.messaging.showMessaging(requireActivity())

The sdk seems well initialized ahead of that as I dont get any error message when the Channel key is properly provided.

in the logcat I can see:

 Failed to create appUser.                                                                          retrofit2.HttpException: HTTP 400 

or 

Creating a new errorState
retrofit2.HttpException: HTTP 400 

Adding a breakpoint in the retrofit code showed up the following api body error:

{"error":{"code":"bad_request","description":"Invalid integrationId or platform."}}

ext {
    minSdkVersion = 24
    targetSdkVersion = 33
    compileSdkVersion = 33
    buildToolsVersion = "33.0.2"
}