There are a few things you can try:
In Settings - Wi-Fi: turn off Wi-Fi and on again.
Also there: tap the network you want to join, choose "Forget this network". Set it up again afterwards.
Another option: reset network settings in Settings - General - Reset. Set up all the connections again afterwards.
Maybe the router is the cause for your issue.
Turn off the router, turn it on again.
Make sure router and iPad are up to date. The latest software for your iPad (2 onwards) is 7.0.4.