Hello @Keng KPT. Pengjui ,
Please note that using an old, unsupported version of Microsoft Entra Connect can cause this error, "Unable to retrieve the Azure Active Directory", please make sure if you are using the latest version of Microsoft Entra Connect.
From the Screenshot which you have shared, I can see the Microsoft Entra Connect version is 2.2.8.0.
Please note that the Microsoft Entra Connect version 2.2.8.0 is an older and deprecated version.
Please refer to the below Screenshot for the latest versions of Microsoft Entra Connect and their end of support date.
All other versions are not supported
If you run a retired version of Microsoft Entra Connect, it might unexpectedly stop working.
To learn more about how to upgrade Microsoft Entra Connect to the latest version, see Microsoft Entra Connect: Upgrade from a previous version to the latest.
Reference document:
Microsoft Entra Connect: Version release history - Microsoft Entra ID
I hope the above information provided is helpful. Please let me know if you have any queries.