Can't log onto my wifi

[MoneyGuy]

I have wifi at home and at my office (I own the business so it's my system entirely). I'm getting on at home fine but a few days ago at work I have been getting a log-in screen to get onto my wifi here using my iPad so I go to settings to enter my password, and the ENTER button is greyed out so I'm unable to log on. It works fine for my iPhone, so it's just on my iPad that I'm unable to get on. I've tried using SETTINGS and also going directly to email or to Safari and neither lets me into my wifi so I'm forced to use 3G. I have rebooted the iPad. Why is the ENTER button greyed out? I've never seen that before.

Any ideas or advice?

 

[MoonlitSonata]

It means the password is too short

 

[MoneyGuy]

But it's greyed out even before I enter any password. Even if I could enter a password, it's the same one I've always had.