Here are a few things to check
- Assuming there is a firewall between your DMZ and internal network, verify which ports are open
- Verify the TCP/IP protocol is Enabled
- Verify the SQL Express port.
Also, which version of SQL Express?
i missed to open the SQL express port which is 50051 in my case
sorry i missed to update here that it is reolved now
i opened incoming port number 50051 on the epo server and i was able to install without issues