Azure Function Event Hub Log forwarder 400 Error

[ioxFR]

Hello,
i'm trying to setup solution to forward logs as i got some appservice docker under linux not supported by datadog appservice extension.
I did the setup as mentionned in the doc using ps1 script
Describe what happened:
When message arrive in eventhub, azure function start.
Azure function try to send log to datadog.com endpoint but failed:
2021-08-05T21:08:40.359 [Error] unable to send request after 2 tries, err: invalid status code 400
2021-08-05T21:08:40.410 [Error] Some messages were unable to be sent. See other logs for details.

I tried why different log format (JSON & csharp)
Azure function got direct internet access, no proxy or something like that.
Code was node changed, the code deployed is the same as the code in github

Describe what you expected:
The azure function should send with success logs to datadog.com

Steps to reproduce the issue:
1 - Deploy eventhub/AZ Function using ps1 script to a tenant
2 - Configure an appservice diagnotics settings to drop logs in eventhub namespace
3 - Generate traffic to app service and observe AZ Function logs

Thanks for your help

Rgds,
Valentin