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Built-in Ethernet wired network card can not be found, so I can not log on APP STORE, there is no way to solve it?
Sadly, the Ethernet hardware is part of the main logic board. So you’ll need to replace the logic board if you want to repair it. But you do have a few connectivity options here! First you do have WiFi so you could try setting up a WiFi access point (AP) 802.11n. Your other option is using a Ethernet USB dongle the only rub here it’s very slow and they are hard to find one that works with OS-X. Then there is always sneaker-net. Use a second mac to access what you want and download it to a FireWire or USB drive and then carry over the drive to your system to then copy over the files.