Thank you for posting in Wired Communities. Based on what you described the issue exists when you connect the Industrial PC APC910 with the Ethernet separator. Just to double check
1) If this is the Ethernet separator you have https://www.pepperl-fuchs.com/global/en/classid_1942.htm?view=productdetails&prodid=32275
2) Can you clarify what is the problem when you said cannot configure it to work in this configuration? Are you referring there is no network connection?
The connection speed you mentioned is 10 Mbps, please check if you can try forcing the speed of 82579LM to 10 Mbps which can be found in the property of the NIC in the device manager. You can go to the device manager->Network adapter->82579LM, right click to go to the property->Advance Setting->Speed and Duplex. Configure the same speed setting on both the 82579LM and the Ethernet Separator. 10 mbps or 100 mbps, or autonegotiation mode both side depends on whichever is applicable in your configuration.
Just to double check which latest driver you are using? We have Windows 7 driver for 82579LM at https://downloadcenter.intel.com/download/18713/Intel-Network-Adapter-Driver-for-Windows-7-?product=47620 but this is generic driver which we cannot gurantee 100% compatibility. It is still recommended to contact your system vendor for the driver for Windows 7 embedded for your system.
Another thing you can check is if there is any compatibility issue with the Ethernet separator with 82579LM, you may check with the Ethenet separator vendor.
As this is an embedded OEM NIC on third party system (APC910), I would recommend you to check with the industrial PC manufacturer they might
customize the NIC to adapt their system. We do not have information what are the changes made thus it is best to contact the system vendor for the support. You may refer to this website for our support opton: https://www.intel.com/content/www/us/en/support/articles/000006628/network-and-i-o/ethernet-products.html
Hope the above information help.
You may post your inquiry at our embedded support below since the 82579LM is integrated on third party system as embedded components. They can further assist from there.