Router Password - too long

I recently got a Venue Pro 11 and set up router at my home with no issues. When I'm trying to connect to my mother's WIFI router, I cannot. The tablet recognizes the router - no question there. The problem is the password.  It is too long. The password has 26 character long. I cannot enter more than 20 or so characters. Is there a way to lengthen or increase the number of characters that I can type?

Thanks for help.