You might have confused "day" and "clay" or "word" and "world" or something like that.
Whether it was
day or
clay, the "
Next" button will still be visible after you reach 12 characters. So the problem isn't a mis-typed word.
I have tried "dog dog dog dog dog dog dog dog dog dog dog dog" (even with double space) and the next button became clickable.
Could it be that you chose "
Import Bitcoin Addresses and Private Keys" rather than "
Standard Wallet"->"
I Already Have the Seed" Option?