Try a different outlet, maybe closer to the router - they can be a bit susceptible to line and RF noise. Since you've had it connected before you know your router is fine - try to avoid changing any settings there, or change it back if you did and it caused the device to disconnect. It might be dead and if so you'll need to contact TP Link.

Sorry for that :(. The wifi doesn't fail all that often though so it might be worth trying a few more things. If it's not flashing after setup it may have completed but your phone re-connected to your 5GHz signal and can't find the switch. Force your phone onto your 2.4GHz signal (rename the 5GHz SSID if necessary) to see if it's there. If it's flashing amber try moving it around - it's struggling to connect. If it's still alternate flashing that's an odd way to fail (wifi is working but can't connect in STA mode?) but I suppose it's possible - I'd try a few different locations to be sure.