WG-C20 Wifi failure after update

[poke612]

Since I do not see a thread about android accessories or "External hard drives" and it should be a product of SONY not xperia, so I put it here (as is also can work with Tablet), please move if it is necessary, 

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Yesterday I received a update of firmware of my WG-C20 which I brought from japan late month. (LINK: http://www.sony.jp/pwserver/update/)

I connect the WG C20 with my Nexus 7 (2012) and update my WG-C20. I am sure that my update is successful since I can connect the device (with my old setting) via wifi successfully after the update.

Later I used the Android app to do the factory reset, and tried to set up the wifi setting of the WG-c20.

After several restarting (since I would like to set up a guest SSID), the device now keep "booting the wifi" status, meaning, the wifi notification light keep blinking. 

The condition cannot be repair even I do a hard reset (Press and long hold the RESET buttom more than 10 seconds)

I believe there should be some problem with the firmware, since if I connect the device with a Windows PC (power off), the PC is able to recognize the device as a card reader, and the battery function of the device is still working.

I am looking for a way to wipe the whole WG-C20 with my PC and flash the firmware from my Windows (via USB). [I actually strongly suggested SONY to have a application run in Windows environment which can able to do a firmware update. Usually, a normal ROUTER like things have that!!! in case a wifi failure!)

Since I am not in Japan now and The local SONY store where I am now did not sell the product and they refused to offer any technical support for that. I email SONY JP asking their assistance, and they have not yet reply me. Hope the technican here could help me solve the problem.