Try to use another cable to access the unit. Anyway, it's at high risk that the device is broken if the power supply is off during upgrading.

Your device is broadcasting SSID, that means it connect proper to your adapter. So press the remote reset button on adapter for 10~15 seconds. For logging in to the device, did you set static IP on...

Do you want to cover indoor or outdoor or both? For indoor application you could use EAP220, refer to http://www.tp-link.com/common/Promo/en/WiFi-Solution/default.html...

Change another CAT5 Ethernet cable or upper level. Once the problem still exists, change the injector/power supply if available. You can try the below to see if the issue improve: 1. Wireless >...

Scheme you post on #3 is not a good idea. Don't take this. Focus back to the deployment on #1. TL-WA7210N+TL-ANT2415D seems OK. But there are factors influence the wireless quality such client number...

Your device is a V3 version, right? You can see the UG of page number 3 that the system led blinking means unit working normally: http://www.tp-link.com/res/down/doc/TL-WA901ND_V3_UG.pdf The reason...