I am having the exact same issue constantly. My tablet and home wifi work perfectly.
It is not a distance problem as I am standing next to the asiair plus..
I held down the reset button for 5 seconds and watched it reboot the wife, but it still would not connect.
Then I noticed that the green light near the power button was off which informed me that there was an I/O problem.
Please advise how to fix this. Thank you.