You should still be able to access the IED regardless of the IEM, How is the customer accessing the IED? Can you please also provide us with some screenshots to have a better understanding?
My current conclusion is the following:
The error message 503 - Service not available - Industrial Edge Management is missleading. The error message is not referring to the IEM, but to a service on the IED which is not running.
We are trying to start a virutal box image on Windows Server. On Windows 10/11 it is working fine. I will stop activities with the virtual box for now on Windows Server.
My wish towards the development team: A more precise error message / screen would be helpful!