After updating iPad to iOS 8, WiFi no longer works
First I'd recommend you to reset your network settings:

Tap Settings → General → Reset → Reset Network Settings

If that doesn't show the new network within 90 seconds of leaving the device scanning for the network, next you might power down the iOS device once after the settings have been reset.

Enough users have the same problem as you see in the official Apple forum as well as here, so it looks like Apple has changed how things work with iOS 8. a.k.a “where there’s smoke there’s fire”

So only "real" solution may be to wait for Apple to fix this with an update.