|This is a little less specific, Have you ever connected to this connection before?|
IF you have try renewing the connection. Under the settings>wireless> there is your network listed (if its broadcasting) and an arrow. tap on the arrow and scroll down to renew lease and click ok.
IF can you see the connection on the ipad and it denies the connection then
1.) ensure that there is a strong wireless signal. (two bars plus preferably three)
2.) selected your wireless connection(often there is more than one if you are in a busy area)
3.)ensured that your key or password was correct. one didget on a key makes a difference and I's and 1's,Bs and 8's look a lot a like in the small printing.