Hi,@walid belhadj
Thanks for posting your question in the Microsoft Q&A forum.
This looks a network configuration problem in your organization.
Can you provide HCW logs and Windows application logs in English? It's useful for us to find the problem.
Based on the current situation, here are my suggestions:
- I would confirm with you that whether there exist firewall or other network filter tools on your on-premises Exchange, if there are, try to turn off the firewall. Then check again.
- You can also use steps below to check the connection between your Exchange on-premises and Exchange online: For more detailed information, you can have a look this article Verify connectivity.
- Download sample script
- Switch EMS to the script location and import the cmdlets by running the following command
Import-Module .\HybridManagement.psm1
- Check the connection with command below:
Test-HybridConnectivity -TestO365Endpoints
3.Restart IIS and restart the server.
If my answer is helpful to you, please mark it as the answer so that other users can refer to it. Thank you for your support and understanding.